Stormwater Quantity Management Plan-2002

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
DCM COPY DCM COPY
lease do not remove!!!!!
Division of Coastal Management
STO.IR-MWATER
QUANTITY
MANAGEMENT
PLAN
TOWN OF CALABASH
CALABASH, NORTH CAROLINA
FEBRUARY 27, 2002

1
STORMWATER QUANTITY
MANAGEMENT PLAN
TOWN OF CALABASH
Calabash, North Carolina
February 27, 2002
' The preparation of this report was financed in part through a grant provided by the North Carolina
Coastal Management Act of 1972, as amended, which is administered by the office of Ocean and
' Coastal Resource Management, National Oceanic and Atmospheric Administration.
Prepared by:
URS Corporation — North Carolina
3109 Poplarwood Court, Suite 301
Raleigh, North Carolina 27604
[phone]
Fax: [phone]

' TOWN OF CALABASH
TABLE OF CONTENTS STORMWATER QUANTITY MANAGEMENT PLAN
Section Page
ExecutiveSummary.........................................................................................................................E-1
Chapter 1 - Purpose and Goals
1.1
Purpose of the Master Plan.......................................................................................................1-1
1.2
Goals of the Plan......................................................................................................................1-1
1.3
Structure of the Plan.................................................................................................................1-2
'
1.4
Methodology............................................................................................................................1-2
Chapter 2 — Regulation/Ordinance Review
2.1
Federal Regulations..................................................................................................................2-1
2.2
State Regulations......................................................................................................................2-4
'
2.2.1 Division of Coastal Management
....................................................................................2-5
2.2.2 Division of Land Resources . .2-6
2.2.3 Division of Water Quality..............................................................................................2-7
2.2.4 North Carolina Division of Highways............................................................................2-9
'
2.2.5 NCDOT Subdivision Roads...........................................................................................2-13
2.2.6 NCDOT Policy on Street and Driveway Access to Highways.......................................2-15
'
2.3
SBWSA Ordinances.................................................................................................................2-16
2.3.1 Stormwater Ordinance....................................................................................................2-16
2.4
Local Ordinances.....................................................................................................................2-17
Chapter 3 — Policy
3.1
Responsibilities........................................................................................................................
3-1
3.2
Stormwater Management.........................................................................................................
3-1
3.2.1 Public Education/Public Involvement............................................................................
3-1
3.2.2 Increased Runoff Due to Development..........................................................................3-1
'
3.3
Drainage System Design, Operation, and Maintenance .......................
3.4
Best Management Practices(BMPs)........................................................................................
3-2
3.5
Floodplain Development..........................................................................................................3-2
Chapter
4 Town Overview
-
'
4.1
4.2
Setting......................................................................................................................................4-1
Hydrography.............................................................................................................................4-1
4.3
Hydrologic and Hydraulic Characteristics...............................................................................4-1
4.3.1 Waterbodies....................................................................................................................4-1
4.3.2 Soils................................................................................................................................4-1
4.4
Land Use..................................................................................................................................4-3
4.5
Effects on Water Quantity........................................................................................................4-3
'
Chapter 5 — Drainage Problem Area Recommendations
'
5.1
Selection Criteria......................................................................................................................5-1
'
02/27/02 i

TOWN OF CALABASH
TABLE OF CONTENTS STORMWATER QUANTITY MANAGEMENT PLAN
Section Page
5.2 Evaluation and Recommendations................................................................................. 5-2
5.3 Operation and Maintenance............................................................................................5-7
Chapter 6 - Stormwater Management Program
6.1 Recommendation Summary .....................................................................................................6-1
6.2 Project Selection Criteria.........................................................................................................6-1
6.3 Capital Improvement Program................................................................................................. 6-2
6.4 Operation and Maintenance Program.......................................................................................6-3
6.5 Funding....................................................................................................................................6-3
Chapter 7 - References
LIST OF APPENDICES
Appendix A Pervious Concrete
Appendix B Stormwater Focus Area Pictures
LIST OF TABLES
Table 4-1
Soils Data
Table 5-1
Recommendations
Table 6-1
Project Selection Criteria and Rankings
Table 6-2
Capital Improvement Program
LIST OF FIGURES
Figure 4-1
Major Drainage Basins
Figure 4-2
Soil Map
Figure 5-1
Drainage Focus Areas
ov27102 11

TOWN OF CALABASH
' EXECUTIVE SUMMARY STORMWATER QUANTITY MANAGEMENT PLAN
The Calabash Stormwater Quantity Management Plan provides an outline of the stormwater quantity
' management policies and actions for the Town of Calabash. This document provides direction for
stormwater quantity management for the Town of Calabash. The starting point for the Plan begins with
the purpose, goals, and objectives described in this summary.
' The purpose of the Calabash Stormwater Quantity Management Plan is to provide a comprehensive
and unified framework for stormwater management which follows the Management Plan, complies
' with all regulations, and includes a Capital Improvement Program that will benefit the entire Town.
The following goals provide the direction in meeting the purpose of improving hydrological functions.
' 1) Evaluate the water quantity problems in the Town and recommend actions to mitigate these
problems.
2) Provide a capital improvement program and outline maintenance actions that incorporate
recommendations from the Plan.
3) Outline an implementation plan for recommended action items.
Policy regarding responsibilities, ordinances, system operation and maintenance, easement acquisition,
and public involvement is described in Chapter Two and Three. The water quantity problems in the
Town are described and action items for these problems are provided in Chapter Five. The policy,
maintenance, and capital improvement action items described in Chapter Six should be considered the
first steps in working to achieve sound stormwater quantity management. Further information such as
detailed tasks for each action item should be addressed in future tasks.
' The recommendations for each area of concern were evaluated based upon the safety and water quantity
benefits provided by the recommended solution. The area determined to be the highest priority was
Hunter's Trace. Flooding due to blocked channels and culverts, along with improper and/or non-existent
roadside swales causes flooding along Harbor Drive and also along Thomasboro Road. The remaining
areas of concern and recommended solutions are described in Chapter Five. The evaluation criteria are
presented in Chapter Six.
Preliminary, order of magnitude cost estimates are provided in Chapter Six. Future adjustments to these
program costs will have to be made as more information (survey, modeling, etc.) is completed.
[1
Additional public input is also important as the stormwater quantity management plan proceeds. Public
education and public involvement is critical to successful Stormwater quantity management.
02/27/02 E-1

�I I
' CHAPTER ONE TOWN OF CALABASH
PURPOSE AND GOALS STORMWATER QUANTITY MANAGEMENT PLAN
' The Calabash Stormwater Quantity Management Plan (Plan) outlines an approach to Stormwater
management for the Town of Calabash (Town). The Plan begins by detailing the purpose, goals, and
objectives described in this chapter.
For a stormwater quantity management plan to be successful, it must have a clear purpose, plus attainable
goals and action items. In order to develop a clear purpose and goals, it is necessary to identify the
problems or potential problems within the watershed. Within the Town, flooding and water quantity
issues have been identified as major problems. The purpose and goals described below provide direction
for the future stormwater management effort to improve these problems.
1 1.1 PURPOSE
The purpose of the Calabash Stormwater Quantity Management Plan is to provide a comprehensive
and unified framework for stormwater quantity management that complies with all regulations and
includes a Capital Improvement Program that will benefit the entire Town.
The purpose of the Plan is to provide a framework for Stormwater quantity management that will restore
hydrological functions within the Town. The framework for stormwater quantity management will
incorporate the policies and procedures already established by the Town, provide new program
' components, and recommend changes to existing ordinances and policies. The implementation of these
recommended policies and projects is an important step to having an effective and substantial program.
' The Plan will identify the components of stormwater quantity management and outline the action items
for implementation. The recommended action items that will help to meet the goals for the program are
described in the next section.
1.2 GOALS OF THE PLAN
The following goals provide the direction in meeting the purpose of improving hydrological functions:
' 1) Evaluate the water quantity problems in the Town and recommend actions to mitigate these
problems.
2) Provide a capital improvement program and outline maintenance actions that incorporate
recommendations from the plan.
3) Outline an implementation plan for recommended action items.
Action items are necessary to carry out the work in achieving these goals. The action items recommended
for each focus area are summarized in Chapter 5.
' 1. Evaluate the water quantity problems in the Town and recommend actions to mitigate these
problems.
This management plan will evaluate the water quantity problems in the Town and discuss recommended
solutions. The solutions may need to be policy decisions that require revisions to the existing ordinances
or actions such as a maintenance project to restore the capacity of an existing ditch.
1
02/27/02 1-1

1
' CHAPTER ONE TOWN OF CALABASH
PURPOSE AND GOALS STORMWATER QUANTITY MANAGEMENT PLAN
' 2. Provide a capital improvement program and outline maintenance actions that incorporate
recommendations from the Plan.
The recommended capital improvements and maintenance actions will be prioritized in order to create a
program that outlines budget requirements. Funding needs will be discussed and future actions with
regard to the stormwater quantity management will be provided.
3. Outline an implementation plan for recommended action items.
An implementation plan for the action items is necessary to ensure that the vision and goals are achieved.
A plan can only succeed if it is implemented and not collecting dust on a shelf.
1.3 STRUCTURE OF THE PLAN
Chapter One - Pufpose and Goals
The purpose and goals have been described and the contents of the plan are listed in this section. The
methodology is provided to describe the basis for the recommendations.
' Chapter Two — Regulation/Ordinance Review
In this chapter, all federal, state, and local ordinances relating to stormwater will be reviewed.
Chapter Three - Policy
In this chapter, the existing policy with regards to stormwater management is described. Changes to
existing policy and new areas requiring a policy decision action are provided.
' Chapter Four —Town Overview
This chapter provides a description of the physical setting and the interaction of land use, soil types, water
features, and hydrology and their effect on water quantity and water quality.
SChapter Five — Watershed Characteristics
The characteristics of the Town, along with the water quantity problems, are described and action items
recommended.
Chapter Six - Stormwater Management Program
The action items from the preceding chapters are summarized. The estimated costs for the recommended
' action items are provided in this chapter. Funding sources are identified.
1.4 METHODOLOGY
The methodology for this Plan is to use existing data to evaluate and recommend the action items
necessary to achieve the stated goals. Problem area locations and descriptions have been obtained from
' Town of Calabash personnel and local citizens.
02/27/02 1-2

Ll
■ CHAPTER TWO
■ REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
Decisions the Town makes now regarding stormwater issues have an effect on storm drains stem
g g Y
performance, system condition, and future water quality. This chapter outlines the existing federal, state
and local regulations and ordinances regarding stormwater management and evaluates the policy changes
that are needed changes to provide effective management in the future.
2.1 FEDERAL REGULATIONS
This section provides a summary of federal regulations that presently define or in the future may affect
stormwater management requirements for the Town. The goal of this review is to identify and summarize
the regulatory and technical issues that must be incorporated into the Town's stormwater management
and development policies. The summarized requirements presented in this section will subsequently be
compared to existing Calabash stormwater management policies with recommended modifications
provided as necessary.
' The Clean Water Act
In 1972, Congress amended the Federal Water Pollution Control Act, referred to as the Clean Water Act
(CWA), to prohibit the discharge of any pollutants to waters of the United States from a point source,
unless the discharge is authorized by a National Pollutant Discharge Elimination System (NPDES)
permit. As pollution control measures for industrial process wastewater and municipal sewage were
implemented and refined, it became evident that more diffuse sources of water pollution were adversely
impacting water quality. In particular, stormwater runoff from large surface areas, such as agricultural
and urban land, was found to significantly impair water quality.
At the Federal level, Sections 401, 402 and 404 of the Clean Water Act require permits for those activities
that might affect water quality either through direct discharge of dredged materials or from runoff. The
most recent Federal Regulations that will significantly impact existing stormwater management practices
are 40 CFR Parts 9, 122, 123, and 124 - National Pollutant Discharge Elimination System (NPDES) —
Regulations for Revision of the Water Pollution Control Program Addressing Storm Water Discharges;
Final Rule (commonly referred to as Phase II Storm Water Regulations).
Phase I NPDES Stormwater Regulations
In 1987, Congress amended the CWA to require implementation of a comprehensive national program for
addressing stormwater discharges. This implementation has occurred in two phases. The first phase,
referred to as "Phase I", was promulgated in November 1990. Phase I requires NPDES permits for
stormwater discharge from a large number of priority sources including:
• Municipal separate storm sewer systems generally serving populations of 100,000 or more.
• Several categories of industrial activity, including construction sites that disturb five or more
acres of land.
Applicability to the Town of Calabash
The South Brunswick Water and Sewer Authority (SBWSA) has received a hybrid Phase I/
Phase H NPDES stormwater permit. This permit covers the Town of Calabash, since they are
located within the SBWSA service area
Phase II Stormwater Regulations
The second phase, referred to as "Phase II", was promulgated in August 1995. These regulations were
1 02/27/02 2-1

1
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
adopted b the EPA in December 1999. Phase II expands the existing stormwater program to include:
P Y
• Discharges of stormwater from smaller municipalities in urbanized areas.
• Construction sites that disturb between one and five acres of land.
Certain sources are excluded from Phase II based on a demonstrable lack of impact on water quality.
This regulation also allows other sources not automatically regulated on a national basis to be designated
for inclusion based on their increased likelihood for local impairment of water quality. Phase II
conditionally excludes stormwater discharges from industrial facilities that have "no exposure" of
industrial activities or materials to stormwater. States with NPDES permitting authority (North Carolina
has permitting authority) can extend NPDES requirements to smaller towns if there is reason to anticipate
that stormwater runoff from those areas has been or may impact high quality waters. Phase II requires
that industrial facilities owned by Small Municipal Separate Storm Sewer Systems (MS4s) obtain
coverage under an NPDES permit by March 10, 2003.
The EPA believes that the implementation of six measures identified for small MS4s should cost
effectively reduce pollutant discharges. In addition, they believe that the implementation of Best
Management Practices (BMPs) at small construction sites will also reduce pollutants in urban stormwater.
Expected benefits include reduced scouring and streambed erosion, improved aesthetic water quality,
' reduced eutrophication of aquatic systems, improved wildlife, improved tourism, and the reduced costs
for siting reservoirs. These six measures and BMPs provide the framework for the program requirements.
The Stormwater Management Program requirements, as required by Phase II, are as outlined below:
• Public Education and Outreach on Stormwater Impacts
• Public Involvement/Public Participation
• Illicit Discharge, Detection, and Elimination
• Construction Site Stormwater Runoff Control
• Post -Construction Stormwater Management in New Development and Redevelopment
• Pollution Prevention/Good Housekeeping for Municipal Operations
Public Education and Outreach on Stormwater Impacts
Under Phase II, operators of small MS4s must implement a public education program or conduct outreach
activities to distribute educational materials to the community. The education programs and/or outreach
activities should inform individuals and households about the impacts stormwater discharges have -on
water bodies and identify the steps that must be taken to reduce stormwater pollution. It is anticipated
that public understanding will foster endorsement of the program. MS4s are encouraged to collaborate
with their States to fulfill the public education requirement. In particular, MS4s are encouraged to work
with any existing State implemented educational programs.
Public Involvement/Public Participation
As part of the Phase II Public Involvement/Public Participation requirement, municipal Stormwater
Management Programs are required to comply with applicable State and local public notice requirements.
The final rule recommends implementing a public participation process to reach out and engage all
economic and ethnic groups. The EPA believes that early and frequent public involvement can expedite
schedules, improve public support, and provide a more successful program.
Illicit Discharge Detection and Elimination
Under the Phase II requirements, any NPDES permit issued to an operator of a regulated small MS4 must,
1 02/27/02 2-2

CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
at a minimum require the operator to develop, implement and enforce an illicit discharge detection and
elimination program. Under this final rule, the NPDES permit will require the operator of a regulated
small MS4 to:
• Develop a storm sewer system map showing the location of all outfalls, and names and location
of all waters of the United States that receive discharges from those outfalls.
• Effectively prohibit through ordinance, or other regulatory mechanism, illicit discharges into the
separate storm sewer system, and implement appropriate enforcement procedures and actions as
needed, to the extent allowable under State, Tribal, or local law.
• Develop and implement a plan to detect and address illicit discharges, including illegal dumping,
to the system.
• Inform public employees, businesses, and the general public of hazards associated with illegal
discharges and improper disposal of waste.
The illicit discharge and elimination program must only address non-stormwater discharges if it falls
under the categories listed below and if the operator of the small MS4 identifies them as significant
contributors of pollutants to its small MS4. These categories include: water line flushing, landscape
irrigation, diverted stream flows, rising ground waters, uncontaminated ground water infiltration,
' uncontaminated pumped ground water, discharges from potable water sources, foundation drains, air
conditioning condensation, irrigation water, springs, water from crawl space pumps, footing drains, lawn
watering, individual residential car washing, flows from riparian habitats and wetlands, dechlorinated
swimming pool discharges, and street wash water.
Construction Site Stormwater Runoff Control
The Phase II final rule requires operators of regulated small MS4s to develop, implement and enforce a
pollutant control program to reduce pollutants in any stormwater runoff from construction activities that
result in land disturbance of one or more acres. Construction activity on sites disturbing less than one
acre must be included in the program if the construction activity is part of a larger common, plan of
development or sale that would disturb one or more acres. The construction runoff control program must
include an ordinance or other regulatory mechanism to require erosion and sediment controls to the extent
practicable and allowable under State, Tribal or local law. The program must also include sanctions to
ensure compliance. The program must also include, at a minimum:
• Requirements for construction site operators to implement appropriate erosion and sediment
control.
• Procedures for site plan review by the small MS4, which incorporate consideration of potential
water quality impacts.
• Requirements to control other waste such as discarded building materials, chemical and sanitary
waste at the site that may adversely affect water quality.
• Procedures for receipt and consideration of information submitted by the public to the MS4.
Post -Construction Stormwater Management in New Development and Redevelopment
Studies and investigations indicate that prior planning and designing for the minimization of pollutants in
stormwater discharges is the most cost-effective approach to stormwater quality management. Under the
Phase II requirements, any NPDES permits issued to an operator of a regulated small MS4 must require
the operator to develop, implement, and enforce a program to address stormwater runoff from new
development and redevelopment projects that result in land disturbance of greater than or equal to one
acre. This also includes projects less than one acre, which are part of a larger common plan of
02/27/02 2-3

1
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
development or sale that discharge into the MS4. The NPDES permit will require the operator of a
P � g P q P
regulated small MS4 to:
• Develop and implement strategies that include a combination of structural and/or non-structural
BMPs.
• Use an ordinance or other regulatory mechanism to address post -construction runoff from new
' development and redevelopment projects to the extent allowable under State, Tribal or local law.
• Ensure adequate long-term operation and maintenance of BMPs.
• Ensure that controls are in place that would minimize adverse water quality impacts.
Pollution Prevention/Good Housekeeping for Municipal Operations
Phase II specifies that operators of MS4s must develop and implement an operation and maintenance
program that includes a training component and focuses on preventing or reducing stormwater from
municipal operations. The program must include government employee training that addresses
prevention measures pertaining to municipal operations such as: parks, golf courses and open space
maintenance; fleet maintenance; new construction or land disturbance; building oversight; planning; and
stormwater system maintenance. The program may use existing stormwater pollution prevention training
materials offered by the State, Tribe, EPA, or environmental, public interest, or trade organizations. The
EPA encourages operators of MS4s to include the following in their programs:
• Implement maintenance activities, maintenance schedules, and long-term inspection procedures
for structural and non-structural stormwater controls to reduce floatables and other pollutants
discharged from the separate storm sewers.
• Implement controls for reducing or eliminating the discharge of pollutants from street, roads,
highways, municipal parking lots, maintenance and storage yards, waste transfer stations, fleet or
maintenance shops with outdoor storage areas, and salt/sand storage locations and snow disposal
areas operated by the MS4.
• Adopt procedures for the proper disposal of waste removed from the separate storm sewer
systems and areas listed above, including dredge spoil, accumulated sediments, floatables, and
other debris.
• Adopt procedures to ensure that new flood management projects are assessed for impacts on
water quality and existing projects are assessed for incorporation of additional water quality
protection devices or practices.
Applicability to the Town of Calabash
The final Phase H regulations, dated December 9,1999, list areas in the United States that require
or may require permitting under the Phase H program. These areas include.
• Urbanized areas of the United States.
• Governmental entities located fully or partially within an urbanized area.
• Governmental entities (located outside of air urbanized area) that must be
examined by the NPDES permitting authority for potential designation.
The SBWSA has received a hybrid Phase F Phase H NPDES stormwater permit. This permit
covers the Town of Calabash, since they are located within the SBWSA service area.
2.2 STATE REGULATIONS
Stormwater management requirements in North Carolina fall under the jurisdiction of the North Carolina
Administrative Code (NCAC), the North Carolina Coastal Area Management Act (CAMA), and the
02/27/02 2-4

CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
North Carolina Sedimentation Pollution Control Act. The associated agencies responsiblef o e ge or the
implementation of stormwater management requirements are the Department of Environment and Natural
Resource (NCDENR); the Sedimentation Control Commission; and the Coastal Resources Commission
(CRC), respectively. Summarized stormwater management requirements for the three agencies are
provided as follows and will serve as the technical basis for recommended modifications to Town
ordinances. The NCDENR, Division of Coastal Management (DCM), Division of Land Resources, and
the Division of Water Quality (DWQ) regulate development and land use activities to protect water
quality. Additionally, the North Carolina Division of Highways has published guidelines for drainage
studies and hydraulic design, and the North Carolina Department of Transportation (NCDOT) has
drainage standards for subdivision highways.
2.2.1 Division of Coastal Management
The Division of Coastal Management (DCM) regulates development activities and stormwater controls
that occur in the 20 coastal counties of North Carolina through the Coastal Area Management Act
(LAMA) (15A NCAC 7H, 7J, & G.S. 133A, Article 7). Any land disturbing activity which occurs in an
area of environmental concern (AEC) must receive a CAMA permit. The DCM reviews proposed
development plans and refers to the local CAMA Land Use Plans and determines if a Major, Minor or
General Permit is required.
A Major permit is required for land disturbing activities which:
• occur in an AEC
• alter more than 20 acres of land
• propose a structural footprint exceeding 60,000 square feet on a single parcel
• require other State or Federal permits
• excavates or drills for natural resources in an AEC or under water
A Minor permit is required when a Major permit is not required. The following activities are exempt
from a Minor permit:
• maintenance and repair (excluding replacement) of existing structure which does not violate
CAMA standards ,
• accessory uses or structures related to the main use of the site that require no electricity,
plumbing, or other service connections and do not exceed an area of 200 square feet
For an exemption from a minor development permit, the project must meet all of the following
exemptions:
• development activities do not disturb more than 200 square feet on land with a slope greater than
10 percent
• threatened or endangered plants and animals must not be removed, damaged or destroyed
• development activities do not alter surface drainage channels
• the form or vegetation of a frontal dune must not be altered
• development activities must be not be within 20 feet of permanent surface waters
• the project must be in compliance with CAMA standards and local land use plans and ordinances
Development activities requiring a CAMA Major Permit may also require one of the following permits
that are issued by the State:
1 02/27/02 2-5

L
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
• permit to excavate and/or fill
• easement in lands covered by water
• water quality certification
2.2.2 Division of Land Resources
The Division of Land Resources requires a Sedimentation and Erosion Control Plan for land disturbing
g
activities greater than one acre (15A NCAC 4B & G.S. 113A, Article 4). The purpose of the
Sedimentation and Erosion Control Plan is to show practices that will be implemented during and after
construction, that will control erosion and prevent sediments from leaving the site. Erosion and
sedimentation control is required regardless of the size of the land disturbance.
Primary requirements for a Sedimentation and Erosion Control Plan are as follows:
• A sufficient buffer zone must be retained or established along any natural water course or lake to
contain all visible sediment to the first 25 percent of the buffer strip nearest the disturbed area.
An undisturbed 25-foot buffer must be maintained along trout waters.
• The angle of cut -and -fill slopes must be no greater than that sufficient for proper stabilization.
Graded slopes must be vegetated or otherwise stabilized within 30 working days of completion of
a phase of grading.
• Off -site sedimentation must be prevented, and a ground cover sufficient to prevent erosion must
be provided within 30 working days or 120 calendar days, whichever is shorter.
Additionally,
• Erosion and sedimentation control measures must be designed to provide protection from a
rainfall equivalent in magnitude to the 10-year peak runoff. In areas where High Quality Waters
(HQWs) are a concern, the design requirement is the 25-year storm.
• Runoff velocities must be controlled so that the peak runoff from the 10-year frequency storm
occurring during or after construction will not damage the receiving stream channel at the
discharge point. The velocity must not exceed the greater of:
1. The maximum nonerosive velocity of the existing channel, based on soil texture.
2. Peak velocity in the channel prior to disturbance.
3. If neither condition can be met, then protective measures must be applied to the receiving
channel.
The law created the Sedimentation Control Commission to develop and administer North Carolina's
sedimentation and erosion control program. This program is implemented by the DENR, Land Quality
Section under the Commission's direction. Authorized local governments or agencies may adopt their
own ordinances; however, local programs must be approved by the Commission and must meet or exceed
the minimum standards set by the state. If their programs are approved, local governments administer and
enforce them. Because these programs vary widely in content and scope, the administering agency
should be consulted to avoid violations of local ordinances.
The state assists and encourages local governments and other state agencies to develop their own erosion
and sedimentation control programs. The DENR reviews local programs as needed to assure uniform
enforcement of the Act.
1 02/27/02 2-6

1
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
As part of the educational requirements of the Sedimentation pollution Control Act, the Sedimentation
Control Commission sponsored development of a design manual for erosion and sediment control
planning. The ESC design manual is a basic reference for the preparation of a comprehensive erosion and
sedimentation control plan and for the design, construction and maintenance of individual practices.
2.2.3 Division of Water Quality
The Classifications and Water Quality Standards Applicable to Surface Water of North Carolina (15A
NCAC 213 & G.S. 143-214.1, 215.1, 215.3 Article 3) defines surface water classifications and provides
development restrictions and buffer requirements. Surface waters in the Calabash area include the
Calabash River.
The following letter system is used to define the "best usage classifications" for waters in the Calabash
area:
rSA Tidal systems designated for shell fishing for market purposes, primary recreation,
aquatic life propagation and survival, fishing, wildlife, and secondary recreation.
HQW (High Quality Waters) Indicates a supplemental classification for waters protected by an
Antidegradation Policy enforced through the NCDENR. These include waters with
excellent ratings based on biological & physical/chemical characteristics, such as NC
Marine Fisheries Commission designated primary nursery areas (PNA) and Wildlife
Resource Commission designated trout waters.
The SA primary classification denotes surface waters, such as the Calabash River, which are suitable for
commercial shellfishing and all other tidal saltwater uses. Supplemental classifications such as HQW
(high quality water) provide added protection for waterbodies.
The Division of Water Quality enforces the Stormwater Management regulation and general statute (15A
NCAC 2H and G.S.143-215.1) and the Water Supply Watershed Protection Act (15A NCAC 213 & G.S.
143-214.5) for the protection of surface waters. These rules were developed to control pollutants in
stormwater runoff, limit impervious surfaces or built upon area, and ensure that adequate stormwater
management practices are implemented.
North Carolina Administrative Code Section 15A NCAC2H.1000
The North Carolina stormwater management regulations are located in Administrative Code Section 15A
NCAC2H.1000. To ensure the protection of surface waters of the State, a stormwater management permit
is required for any development activities which require a CAMA major development permit (see Section
3.2 of this report) or a Sedimentation/Erosion Control Plan (see Section 3.3 of this report) and which meet
any of the following criteria:
1. Are located in the 20 coastal counties.
2. Drain to Outstanding Resource Waters (ORW).
3. Drain to High Quality Waters (HQW).
1 02/27/02 2-7

I
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
Calabash is included in the 20 coastal counties (Brunswick County) and is subject to permitting
requirements as specified in 15A NCAC 2H.1005. Permitting requirements as specified in 15A NCAC
2H.1005 are described in the following paragraph.
Stormwater Permitting Requirements: Coastal Counties
Stormwater management permits for development activities within the 20 coastal counties fall into one of
the three following categories:
1. Development activities that drain to Outstanding Resource Waters (ORW).
2. Development activities within one-half mile of and draining to SA (saltwater shell fishing and
primary recreation) waters or unnamed tributaries to SA Waters.
3. Development activities in areas except those defined in items l and 2.
The Calabash River is an SA water, therefore permitting requirements are as specified by category 2.
Calabash Permitting Requirements (SA Waters)
Permitting requirements for the Town's SA waters are classified according to low density and high
density options. Permitting requirements for the two options are summarized as follows:
Low Density Option
1. Built -upon area of 25 percent or less; or proposed development of single family residences on
lots with one-third of an acre (14,520 square feet) or greater with a built upon area of 25
percent or less.
2. Stormwater runoff transported primarily by vegetated conveyances; conveyance system shall
not include a discrete stormwater collection system as defined in 15A NCAC 2H.1002.
3. Curb and gutter systems are allowed as specified in 15A NCAC 2H.1008(g). If curb and
gutter systems are provided, a flow spreader mechanism must be located at the swale entrance
and a signed Operation and Maintenance Plan must be provided.
4. A vegetative buffer at least 30-feet wide between impervious areas and surface waters.
High Density Option
1. No direct outlet channels or pipes to SA waters unless permitted in accordance with 15A
NCAC 211.0126.
2. Stormwater control systems must be infiltration systems designed in accordance with 15A
NCAC 2H.1008.
3. Stormwater control systems must be designed to control runoff from all surfaces generated by
one and one-half (1.5) inches of rainfall.
4. Runoff in excess of the design volume must flow overland through a vegetative filter with a
minimum length of 50 feet.
Best Management Practice (BMP) Design Criteria
North Carolina's approach to stormwater quality management in the 20 coastal counties is based first on
minimizing impervious surfaces and, secondly, on treating stormwater runoff from these surfaces. The
State uses a pollutant removal BMP design standard of 85 percent removal for total suspended solids
(TSS).
02/27/02 2-8

CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
A stormwater BMP design manual was published b NCDENR in April 1999. The manual includes
g P Y P
design criteria and TSS removal efficiencies for stormwater BMP types recommended by the State.
As described above, the State requires specific types of stormwater BMPs for low density and high -
density development in the 20 coastal counties. Design criteria for BMPs are outlined in 15A NCAC
2H.1008.
2.2.4 North Carolina Division of Highways
Guidance in methods, policies, procedures, and criteria that must be followed during highway drainage
studies and hydraulic designs is provided in the North Carolina Division of Highways, Guidelines for
Drainage Studies and Hydraulic Design document. Information from this document is pertinent to the
development of recommended Town stormwater management policies since a portion of NC 904 is
located on the island portion of Calabash.
General Drainage Policies and Practices
North Carolina long adhered to the Civil Law Rule in regard to surface water drainage. This rule
obligates owners of lower land to receive the natural flow of surface water from higher lands. It subjects
a landowner to liability whenever he interferes with the natural flow of surface waters to the detriment of
another in the use and enjoyment of his land. Since almost any use of land involves some change in the
drainage and water flow, a strict application of the civil law principles was impracticable in a developing
society. Thus, a more moderate application of this rule to allow a landowner reasonable use of his
property evolved.
The North Carolina Supreme Court formally adopted the Rule of Reasonable Use with respect to surface
water drainage and abandoned the Civil Law Rule (Pendergrast V. Aiken) in August 1977. The adopted
Reasonable Use Rule allows each landowner to make reasonable use of his land even though by doing so,
he alters in some way the flow of surface water thereby harming other landowners. Liability is incurred
only when this harmful interference is found to be unreasonable and causes substantial damage.
There are still some unanswered questions in the application of the adopted Reasonable Use Rule to
specific areas of State agency activities. However, the rule is in line with the realities of modern life and
will provide just, fair and consistent treatment. Therefore, the policies and practices of the Division of
Highways in regard to surface drainage matters follow this rule.
Engineer's Responsibility
The Reasonable Use Rule places responsibility on the "landowner" to make reasonable use of his land.
While "reasonable use" is open for interpretation on a case -by -case basis, it would certainly infer from an
engineering standpoint that provisions for, and treatment of, surface waters on the property are made in
accordance with sound, reasonable and acceptable engineering practices. Therefore, the policies and
practices of the Division of Highways in regard to surface drainage matters follow this rule.
The rule also states that liability incurs only when harmful interference with the surface water is found to
be unreasonable and causes substantial damage. Therefore, it is incumbent on the Engineer to evaluate
the potential effects of surface water activities on both upstream and downstream properties and to
include provisions in the design to hold these effects to reasonable levels.
1
02/27/02 2-9

11
1
L
1
ri
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
Augmentation, Acceleration
Development of property can cause an increase in the quantity and peak rate of flow by increasing
impervious areas and providing more hydraulically efficient channels and overland flow. It is the policy
of the Division of Highways to develop and make reasonable use of its lands and rights -of -way through
sound, reasonable and acceptable engineering practices and to deny responsibility for augmented
accelerated flow caused by its improvements unless determined to cause unreasonable and substantial
damage. It is likewise the policy of the Division of Highways to expect this same practice and acceptance
of responsibility by other property owners and those engaged in the development of these properties.
Diversions
Diversions are defined as the act of altering the path of surface waters from one drainage outlet to
another. It is the policy of the Division of Highways to design and maintain its road systems, so that no
diversions are created, insofar as is practicable from good engineering practice.
Any person(s) desiring to create a diversion into any highway rights -of -way shall do so only after
receiving written permission. This permission will be granted only after it has been determined that the
additional flow can be properly handled without damage to the highway, that the cost for any required
adjustments to the highway system will be borne by the requester, and that appropriate consideration and
measures have been taken to indemnify and hold harmless the Division of Highways from potential
downstream damage claims. It is Division of Highways policy not to grant diversions unless refusal
would create a considerable and real hardship to the requesting party.
Improvements and Maintenance of Drainage Within the Rijzht-Of-Way
Drainage structures and ditches shall be kept open and maintained at a functioning level such that they do
not present an unreasonable level of damage potential for the highway or adjacent properties.
Where the elevation of the flow -line of an existing culvert under a highway is not low enough to
adequately provide for natural drainage, the Division of Highways will assume full responsibility for
lowering the culvert or otherwise provide needed improvement.
Where a requested culvert invert adjustment is a result of a property owner lowering the flow -line of the
inlet and outlet ditch in order to improve drainage of his property, the following considerations shall be
given to the action taken:
• The lowered drain must have a reasonable expectancy of being functional and maintainable.
• Division of Highways participation (up to full cost) must be based on benefit gained by the
roadway drainage system as a result of the lowering.
• Where the new installation is of doubtful benefit, or of no benefit to highway drainage, the
requesting party must bear the entire cost of installation.
Where the size of an existing highway culvert is determined to be of unacceptable adequacy in regard to
the roadway system functioning as a result of a general overall development of the watershed, it is the
Division of Highways responsibility to replace the structure or otherwise take appropriate action. Where
this same culvert inadequacy is the result of a single action or development, it is felt to fall within the
�- realm of "unreasonable and substantially damaging" under the State adopted drainage ruling. Therefore,
the party responsible for the action or development should bear the cost of replacement.
02/27/02 2-10

I
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
Where a new culvert crossing is requested, if the culvert is required for proper highway drainage or
sufficient benefits to the highway drainage system would occur, the full cost will be borne by the Division
of Highways providing there is no diversion of flow involved. Where the new installation is of doubtful
or no benefit to highway drainage, the property owner will bear the entire cost. When both parties receive
benefit, a joint effort may be negotiated.
Established culvert crossings will be maintained and requests to eliminate any culverts should have
approval from the State Hydraulics Engineer.
When new private drives are constructed entering the highway, the property owner can furnish, delivered
to the site, the amount, type and size pipe designated by the Division of Highways, to be installed by
maintenance forces.
No alteration, attachment, extension, nor addition of appurtenance to any culvert shall be allowed on
highway rights -of -way without written permission.
Improvements and Maintenance of Drainage Outside the Right -Of -Way
While it is the responsibility of the Division of Highways to provide for adequate drainage for
constructing and maintaining the State Highway System, it is not its policy nor responsibility to provide
improved drainage for the general area traversed by such roads, unless incidental to the drainage of the
road or highway itself. Drainage involvement outside the highway rights -of -way is limited to two general
areas of justification:
• Sufficient benefit would be gained by such action to warrant the cost. These benefits would be in
such areas as reduction in roadway flood frequency or extent, facilitation of maintenance, or a
reduction in potential damages.
• Work is required to correct a problem or condition created by some action of the Division of
Highways.
It is not the responsibility of the Division of Highways to eliminate flooding on private property that is
not attributable to acts of the agency or its representative.
In general, outlet ditches will be maintained for a sufficient distance below the road to provide adequate
drainage. On large outlets serving considerable areas outside the right-of-way, the maintenance should be
done on a cooperative basis, with the benefited properties bearing their proportionate share. Shares will,
in general, be based on proportioning of runoff from the areas served by the outlet.
It is not the policy of the Division of Highways to pipe inlet or outlet drains, natural or artificial, outside
the right-of-way, which existed as open drains prior to existence of the highway. Where the property
owner wishes to enclose an inlet or outlet, the Division of Highways may install the pipe adjacent to the
right-of-way if justified by reason of reduced maintenance, safety or aesthetics, if the pipe is furnished at
the site by the property owner. This does not apply to the development of commercial property.
Obstructions
It is the policy of the Division of Highways that when a drain is blocked below the highway, which is
detrimental to highway drainage, if from natural causes, the Division of Highways will take necessary
measures to remove the block or obstruction. Where the block is caused by wrongful acts of others, it is
the policy of the Division of Highways to take whatever recourse deemed advisable and necessary to
1
02/27/02 2-11

I
LJ
1
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
cause the party responsible to remove the block. Where a block occurs downstream of a highway,
whether natural or artificial, and is of no consequence to the Division of Highways, it is their policy to
remain neutral in causing its removal.
Drainage Easements
Where runoff is discharged from the right of way at a point where there is no natural drain or existing
ditch, a permanent drainage easement is required to allow construction of a ditch or channel to convey the
discharge to an acceptable natural outlet. When the discharge is into a natural drain or existing ditch and
the increase in flow would exceed the capacity or otherwise create a problem, a temporary drainage
easement can be obtained to allow enlarging or otherwise improving the drain to a point where the
increase in discharge will not cause damage. It is generally preferable that any structural feature such as a
drop inlet, catch basin, or pipe -end be contained within a permanent easement.
Subdivision Streets
When roads and streets built by others are accepted onto the system for maintenance, responsibility for
the drainage system, discharge pattern and outlet locations is as it existed at the time of acceptance and is
limited to the rights -of -way.
Hydroloey
The hydrological analysis phase involves the determination of discharge rates and/or volumes of runoff
that the drainage facilities will be required to convey or control. Many hydrological methods are
available and most can be appropriately and effectively used under proper control and application. When
the site involves a Federal Emergency Management Act (FEMA) flood study area, discharge methods and
values provided in the report will take precedent over these methods for determining compliance with the
regulation. The results from any hydrologic procedure should be compared to historical site information
and adjustments made in the values estimated or procedure used when deemed appropriate. The designer
must also consider potential future land use changes within a watershed over the life of a roadway
structure and include this effect when estimating design discharges.
Method for Calculating Peak Discharge
If a watershed less than 10 acres is primarily composed of pavement, grassed shoulders and slopes, and/or
other mixed surface type runoff, the rational formula should be used for discharge determination.
Highway Design Discharge Criteria
One specific criterion on which the design is evaluated and generally referred to as the "design discharge"
is the flood level and frequency which results in inundation of the travelway. The minimum desirable
levels of protection from travelway inundation by roadway classification are listed as follows:
I
11
Roadway Classification Frequency
Interstate (I) 50 year
Primary (US & NC) 50 year
Secondary (Major, City thoroughfare) 50 year
Secondary 25 year
Culvert Design Criteria
There are four discharge levels that must be evaluated for each culvert design. These are:
(1) The "design discharge".
1 02/27/02 2-12

CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
(2) The Q100 base flood.
(3) Q-overtopping. This discharge is computed after a trial size is selected.
(4) Q10 for outlet protection and erosion control measures.
Other discharges may be required on a site -specific basis. Examples are:
(1) Q-average. For permit determination.
(2) Q-bank full. For fish passage, channel stability or floodplain analysis.
Storm Drainage System Design Criteria
The purpose of a storm drainage system is to collect and transport stormwater runoff from the highway to
an outlet. The complete system consists of the curb and gutter, inlet structures, lateral and trunk line
pipes, and junctions and manholes. The design process for storm drainage systems usually follows the
basic steps of planning/data collection, hydrologic/hydraulic design, and outfall analysis.
Design Frequency
Roadway inlet location, capacities and gutter spread is to be analyzed using a standard rainfall intensity of
four inches/hour. The storm drain pipe system is to be designed using a Q10 discharge with a minimum
time of concentration of 10 minutes assuming 100 percent pick-up at each inlet.
In sag areas where relief by curb overflow is not provided, the system standard design level (Q25 — Q50)
is to be used for analysis to ensure traffic flow is not interrupted.
Pipe System
Storm drain pipes shall be concrete unless a site limitation such as grade or corrosive conditions dictate
I the use of an alternate material. The minimum pipe size to serve a single inlet is 12 inches. For more
than one inlet, or a length of more than 100 feet, a 15-inch pipe is the minimum size. When differing size
pipes enter and exit a junction, the desired practice is to match the crowns of the pipes.
Roadside Ditches
A roadside ditch is a man-made channel generally paralleling the roadway surface and distinguished by a
regular geometric shape. Roadway ditches are to be designed to contain as a minimum the Q5 (5-year)
flow. The typical roadway ditch section is established with sufficient depth to drain the pavement
subbase and flat side slopes for safe vehicle traversability. This generally provides very generous
capacity for the design flow requirements. Therefore, actual capacity determination can be done on a
selective basis at sites on common project grades to verify adequacy and establish limitations on the
length of the ditch run.
The size requirements of the project special side ditches along the toes -of -fill will be established based on
an analysis of the design flood. This ditch capacity analysis will be performed using Mannings' equation.
The roadway section including shoulders and slopes shall be considered an urban watershed.
2.2.5 NCDOT Subdivision Roads
A subdivision road is one that serves a parcel or tract of land that is subdivided into two or more lots,
building sites or other divisions for sale or building development for residential purposes where such
subdivisions include a new road or change in an existing road.
1
02/27/02 2-13

I
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
Subdivision roads may be designated public or private. Public designations will be built to minimum
construction standards of the North Carolina Department of Transportation (NCDOT) as required under
North Carolina General Statute 136-102.6. Private roads need not meet minimum construction
requirements, but must meet minimum construction requirements before ever becoming a part of the
State -maintained system.
NCDOT Subdivision Roads Drainage Design and Construction Requirements
Design criteria for NCDOT subdivision roads are provided in Subdivision Roads — Minimum Design
Standards. Drainage design and construction requirements for state -maintained subdivision roads are
summarized for review purposes in the following paragraphs.
Requirements for Addition of Subdivision Roads to the State Sy stem
• Erosion and Sedimentation — All subdivision roads shall have an acceptable permanent vegetative
cover established and other acceptable permanent erosion control measures installed in
accordance with Division of Highways specifications, prior to addition to the State System.
• All pipe culverts, storm sewers and appurtenances shall be free of all debris and silt build-up and
shall be structurally and hydraulically sound, and functioning in a normal manner. All drainage
ditches shall be of such a width and depth and with such a slope as to carry the anticipated
discharges. Paved ditches or riprap shall be required where necessary.
Minimum Drainage Requirements for Subdivision Roads
The Division of Highways shall review all drainage prior to acceptance of any facility to the State
System. All storm drainage shall be adequate so that the road may be maintained without excessive cost,
and not cause flooding on private property from storm runoff of the design frequency. Permanent
drainage easements may be required. The minimum design frequency shall be as follows but may be
increased at the recommendation of the State.
Storm sewer collector - 10 years
Cross drainage — 25 years
In areas where ditch grades or quantities of flow deem it impracticable to establish and maintain
vegetation, an erosive resistant lining such as paving or rock riprap may be required. Subsurface drainage
shall be adequate to maintain a stable subgrade.
,. When road crossings are within areas designated as flood hazard areas under the Federal Flood Insurance
Program, the design must be approved by the responsible local governing agency for its consistency with
local flood zoning ordinances.
Minimum Criteria for Curb and Gutter Deskon
Minimum design criteria for curb and gutter include the following:
• All curb and gutter sections must meet Division of Highways standards.
• The standard 2' x 6" concrete curb and gutter is the preferred type to be used. Types of other
curb may be used provided the 6" height is maintained.
• The concrete Valley Gutter is an allowable type.
1 02/27/02 2-14

1
1
1
f
I
t
1
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
• Any other types of gutter will be subject to the approval of the Division Engineer after review on
an individual basis. Approval will be subject to the terrain factors in the area under study as they
relate to potential maintenance problems.
2.2.6 NCDOT Policy on Street and Driveway Access to Highways
The North Carolina Department of Transportation has deemed it necessary to regulate the location,
design, construction, and maintenance of street and driveway connections to the State Highway System
for the purpose of protection for such highways, economy of maintenance, preservation of proper
drainage, safe and efficient movement of traffic thereon, and full utilization of the taxpayer's investment.
The objective of this Policy is to establish uniform criteria governing such location, design, construction,
and maintenance. Drainage requirements for street and driveway access to highways are summarized for
review purposes in the following section.
Drainage Requirements for Street and Driveway Access to Highways
Driveways must be constructed so that they do not adversely affect the highway drainage or drainage of
the adjacent properties. The drainage and the stability of the highway subgrade must not be impaired by
driveway construction or roadside development. In no case may the construction of a driveway cause
water to flow across the highway pavement, or to pond on the shoulders or in the ditch, or result in
erosion within the right-of-way.
(1) Drainage collected by ditches, gutters, or pipes on private property shall not be
discharged into the highway drainage system unless expressly approved by the Division
of Highways. The applicant may be required to submit a drainage study to the Division
of Highways justifying the drainage system proposed and the pipe or sewer sizes to be
used. Natural drainage laws and practices must be observed.
(2) Where the construction of a driveway necessitates crossing a highway ditch, a culvert
pipe shall be installed in the ditch. The low point of the driveway profile shall be at or
close to the ditch line. Under no circumstances will existing ditches or gutters be filled
without adequate alternate provisions for drainage being made.
(3) Culvert pipe shall be of a size adequate to carry the anticipated flow in the ditch as
determined by the Division of Highways and shall not be smaller than 15 inches, inside
diameter.
(4) The structural material and gauge of the driveway culvert pipe shall be adequate to
withstand the loads from the anticipated vehicular traffic across the driveway. The
culvert shall meet or exceed the requirements of the North Carolina Standard
Specifications for Roads and Structures. The length of the culvert may be determined as
the sum of the width of the driveway (surface width and shoulder) at the ditch line and
the length needed to accommodate a sideslope of at least 1 vertical to 3 horizontal from
the driveway grade to the ditch. A minimum 20 feet of pipe shall be used on all
commercial and residential subdivision driveways. Plastic pipe is not acceptable for
drainage purposes.
1 02/27/02 2-15

1
1
I
1
I
1
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
(5) Where headwalls or wingwalls are constructed with drainage facilities, a minimum
roadway clearance of 30 feet, measured from the edge of pavement, should be observed
unless protected by guardrail. The use of flared -end sections should be encouraged.
(6) All drainage structures deemed necessary by the Division of Highways, including
incidentals, shall be furnished by the applicant. The Division of Highways will install the
drainage pipe for the applicant at the current rate of installation. If, however, the
applicant makes the installation, the Division of Highways is required to inspect the
installation, and the applicant will be appropriately charged for the inspection. One
inspection fee will be charged for each application, regardless of the number of
installations involved, provided all installations are available for inspection.
2.3 SBWSA ORDINANCES
2.3.1 Stormwater Ordinance
SBWSA has adopted a stormwater ordinance and stormwater ordinance amendment, which apply to the
Town of Calabash, since it is located within the SBWSA planning area. Additionally, the SBWSA
ordinance and ordinance amendment are a part of the SBWSA NPDES Stormwater Permit requirements.
Stormwater management requirements are identified according to low density and high density options,
and whether the area to be developed drains to SA waters. This ordinance reflects the State requirements,
though it is more restrictive. The SBWSA ordinance (with the amendment) also requires that runoff from
all new development, regardless of size, shall approximate the rate of flow and timing of runoff that
would have occurred following the same rainfall under predevelopment conditions for two (2) year and
ten (10) year frequency rainfall events.
For all development draining to SA waters, the requirements of the ordinance (as amended) are
summarized below:
Low Density Option
1. For all lots greater than one acre: Built -upon area of 25 percent or less.
2. For all lots less than one acre:
(a) Lots up to 5,000 square feet — Built -upon area of 25 percent or less
(b) Lots of 5,001 to 10,000 square feet - Built -upon area of 21 percent or less
(c) Lots of 10,001 to 25,000 square feet - Built -upon area of 18 percent or less
(d) Lots of 25,001 to less than one acre - Built -upon area of 15 percent or less
3. Stormwater runoff transported primarily by vegetated conveyances; conveyance system shall
not include a discrete stormwater collection system.
4. A vegetative buffer at least 30-feet wide immediately adjacent to waterbodies.
High Density Option
1. No direct outlet channels or pipes to SA waters unless permitted in accordance with 15A
NCAC 2H.0126.
2. Stormwater control systems must be infiltration systems designed in accordance with 15A
NCAC 2H.1008.
02/27/02 2-16

1
1
1
1
h
1
A
jI
A
I
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
3. Stormwater control systems must be designed to control runoff from all surfaces generated by
one and one-half (1.5) inches of rainfall.
4. Runoff in excess of the design volume must flow overland through a vegetative filter with a
minimum length of 50 feet.
BMP Design Criteria
SBWSA has a draft stormwater drainage design manual. This manual includes design criteria and
recommendations. The manual should be finalized in 2002.
2.4 LOCAL ORDINANCES AND POLICIES
The local ordinances are critical in regulating development through zoning and planning. The local
ordinances should control the density of development and establish building codes consistent with sound
environmental practice. The following provides a summary of some of the zoning and subdivision
ordinances for the Town of Calabash.
The Town of Calabash has the following ordinances in place to control development:
• Zone R-15 Residential: minimum lot size of 15,000 square feet.
• Zone R-8 Residential: minimum lot size of 8,000 square feet for first dwelling unit, 4,000 square
feet for each additional dwelling unit, or 10,000 square feet for a nonresidential unit.
• Zone R-6 Residential: minimum lot size of 6,000 square feet for first dwelling unit, 3000 square
feet for each additional dwelling unit, or 10,000 square feet for a nonresidential unit.
• Zone MFH 1: minimum lot size of 6,000 square feet.
• Zone CB Central Business District: No minimum lot size.
• Zone HC Highway Commercial District: minimum lot size of 10,000 square feet.
• Zone ID Light Industrial District: minimum lot size of 1 acre
• Zone MFH II: minimum lot size of 6,000 square feet.
Zone MFH III: minimum lot size of 4,800 square feet.
• Zone CD Conservation District: minimum lot size of 5 acres.
• 35-foot building height restrictions for all zones.
The Town of Calabash adopted an ordinance relating to flood damage prevention.
Flood Damage Prevention Ordinance
The intent of the ordinance is to promote the public health, safety and general welfare and to minimize
public and private losses due to flood conditions in specific areas by restricting or prohibiting uses in
certain areas, require that uses vulnerable to floods be protected against flood damage, controlling the
alteration of natural flood plains and protective barriers, controlling filling, grading, dredging and other
development which may increase erosion or flood damage, and by preventing or regulating the
construction of devices which will naturally divert flood water or increase flood hazard to other lands.
Stormwater Ordinance
The Town has adopted the SBWSA's Stormwater Ordinance.
02/27/02 2-17

Ll
11
I
A
CHAPTER TWO
REGULATION/ORDINANCE TOWN OF CALABASH
REVIEW STORMWATER QUANTITY MANAGEMENT PLAN
CAMA Land Use Plan
Statements of local policy on land use issues which affect the Town of Calabash are grouped in five
general categories including:
• Resource Protection Issues
• Resource Production and Management Issues
• Economic and Community Development Issues
• Continuing Public Participation Policies
• Storm Hazard Mitigation, Post -Disaster Recovery, and Evacuation Policies
Policies from each of these categories that affect stormwater management are discussed in the following
paragraphs.
Areas of Environmental Concern (AECs)
According to the policy statement regarding AECs, the Town of Calabash "will promote conservation
and management of the Estuarine System as a whole which includes the individual subsystems of
coastal wetlands, estuarine waters, public trust waters, and estuarine shorelines". Such development
must be compatible so as to minimize the likelihood of significant loss of private property and public
resources. Stormwater management measures will be implemented so as to comply with the Town's
policies regarding AECs.
Stormwater Runoff
The Town recognizes the value of water quality maintenance with regard to protecting commercial
and recreational fishing resources and providing clean water for other recreational purposes. The
Stormwater Management Plan will provide another tool for the Town to reduce stormwater pollution
to the waterways and enhance the water quality in the area.
Residential. Commercial, and Industrial Land Development Impacts on Anv Resources
The Town's policy is to protect the Town from adverse development and growth and to guide new
development away from AECs and hazardous areas. The Stormwater Management Plan will be a tool
the Town can implement to help ensure there is no degradation of resources due to stormwater runoff
from these developed areas.
Types of Urban Growth Patterns Desired
The Town would like to maintain its "fishing village" atmosphere. Implementation of the Stormwater
Management Plan will not affect the desired growth patterns in the Town. The Plan will help to
improve visual aspects in the Town (reducing or eliminating standing water during storms), which
will help encourage the desired growth patterns.
Redevelopment of Developed Areas, Including the Relocation of Threatened Structures
The Town supports redevelopment of previously developed areas. It is Town policy that density
allowances for redevelopment areas conform to existing Town building and zoning regulations.
Continuing Public Participation
Town policy is to assure that all residents have a full and adequate opportunity to be informed of and
participate in the Town's planning decision -making process. The Stormwater Management Plan also
includes public education and public participation.
1 02/27/02 2-18

d
CHAPTER THREE TOWN OF CALABASH
POLICY STORMWATER QUANTITY MANAGEMENT PLAN
This chapter outlines the existing Town policies regarding stormwater management and evaluates what
policies need changes for effective management in the future. Current Responsibilities of the Town are
explained in this chapter.
■ 3.1 RESPONSIBILITIES
Stormwater management in the Town of Calabash is currently the responsibility of the State of North
Carolina, the SBWSA, and the Town.
Currently the Town has the following responsibilities regarding stormwater management:
• Inspection of new subdivisions for compliance with subdivision ordinances, including Stormwater
drainage systems.
• Approval of site plans with respect to setbacks from the mean high water mark.
• Inspection of sites for compliance with the Town's Flood Ordinance.
1 3.2 STORMWATER MANAGEMENT
The Town has adopted the SBWSA stormwater ordinance. SBWSA also has developed a stormwater
ordinance amendment, which the Town should look to adopt. The stormwater ordinance helps prevent
illicit discharges and dumping into the storm drains. The ordinance makes it illegal to put gasoline, oil,
antifreeze, and other pollutants into the storm drain system. It is also illegal for any person to put
anything in the ditch, storm drain, or other drainage way that impedes or interferes with the free flow of
stormwater. Additionally, the stormwater ordinance also assists in limiting the amount of impervious
surface on lots, thus reducing the quantity of Stormwater entering the storm drain system, and help to
w reduce the risk of flooding during storms.
3.2.1 Public Education/Public Involvement
This Stormwater Quantity Management Plan provides a way for the Town to improve Stormwater
quantity management in the future and to reduce deficiencies of the storm drain system. An important
part of the plan is educating citizens about stormwater runoff and ways that they can reduce stormwater
runoff to help decrease flooding. Information could be supplied to the public as handouts provided at
Town Hall or real estate offices.
The Town should also work with SBWSA on public education/involvement activities. Public Education
and Involvement are a requirement of SBWSA's NPDES permit and the Town, working with SBWSA
could include information about stormwater quantity management, while SBWSA educates the public
about Stormwater quality management.
3.2.2 Increased Runoff Due to Development
As land is developed, the area of perviousness usually decreases. This decrease accelerates the runoff of
rainfall and increases the peak rates of flow. If measures are not taken during design, this increased rate
of flow can cause flooding and erosion and sedimentation problems. The use of structural BMPs can
provide a solution, as can the implementation of a stormwater ordinance.
02/27/02 3-1

CHAPTER THREE TOWN OF CALABASH
POLICY STORMWATER QUANTITY MANAGEMENT PLAN
3.3 DRAINAGE SYSTEM DESIGN, OPERATION AND MAINTENANCE
A stormwater drainage system consists of manmade conduits and channels and natural ponds, streams,
creeks, rivers, and floodplains. Flooding is the most noticeable problem that occurs with poorly designed
or maintained drainage systems. North Carolina Department of Transportation design criteria, along with
SBWSA design criteria has been reviewed for applicability in the service area and these criteria were
summarized in Section 2. These design criteria, along with NCDENR stormwater design criteria are
excellent references and should be followed by the Town during design and construction of additional
stormwater management measures.
It is important that the Town has an easement for its storm drain systems so maintenance and repairs can
be performed when necessary. For Town -owned storm drain systems carrying runoff from public right-
of-way, the Town may want to obtain an easement for any pipe, inlet, manhole, and outfall. Storm drain
systems which only carry runoff from private property are considered private systems and the Town is not
responsible for their maintenance. For existing inlets and pipes that carry runoff from Town streets, the
Town should try to obtain easements for the pipes and inlets.
The Town should coordinate with SBWSA for operation and maintenance. Since BMPs often serve to
improve both water quality and water quantity problems, a joint effort for operation and maintenance may
be possible. Additionally, SBWSA is developing a drainage system inventory. This inventory will
include type, location, size, material, slope, length, condition, and current ownership. All areas of the
system will be put on a schedule that identifies what type of maintenance needs are to be performed and
how often it should be done. A contingency plan will be developed that outlines what maintenance
activities are needed after a major storm or hurricane.
The Town should look at developing a step-by-step procedure for responding to minor maintenance and
repair requests should also be developed. The amount of major and minor maintenance work performed
will need to be tracked as a way to evaluate Stormwater Management Program success.
3.4 BEST MANAGEMENT PRACTICES (BMPs)
BMPs are methods or practices that can effectively reduce stormwater flooding. Structural control BMPs
described in the North Carolina Department of Environment and Natural Resources Stormwater
Management Guidance Manual include:
• infiltration trenches basins
• dry detention basins
• wet retention basins
• grassed swales
• filter strips
1 3.5 FLOODPLAIN MANAGEMENT
The Town of Calabash has an ordinance that regulates development in the floodplain and they participate
in the Federal Flood Insurance Program. As part of this program, if a building is located in a flood prone
area, the ground floor elevation must be certified before a building permit can be issued.
02/27/02 3-2

CHAPTER THREE TOWN OF CALABASH
POLICY STORMWATER QUANTITY MANAGEMENT PLAN
No changes are recommended to the existing floodplain practices and policies regulated by the Town.
Any drainage system improvements proposed in the floodplain will have to comply with the existing
requirements.
I
1
1
0
1
1 02/11/02 3-3

CHAPTER FOUR TOWN OF CALABASH
TOWN OVERVIEW STORMWATER QUANTITY MANAGEMENT PLAN
4.1 SETTING
The Town of Calabash is located in southwestern Brunswick County, North Carolina. The Town is a mix
of both residential development and commercial businesses. The Town of Calabash has year-round
residents with an increase in population during the summer months due to seasonal tourism. Figure 4-1
shows the town limits of Calabash.
4.2 HYDROGRAPHY
The Town is located in the southeastern portion of the Lumber River Basin that flows from North
Carolina into South Carolina. This river basin is comprised of smaller watersheds or hydrological units
(HUs). The primary water features include Calabash Creek, the Atlantic Intracoastal Waterway (AIWW),
and the Little River Inlet marsh systems, and the Atlantic Ocean.
The Town of Calabash lies within the United States Geological Survey (USGS) Carolina Coastal
watershed and the Waccamaw River watershed. These watersheds have 8-digit hydrological unit code
(HUC) of 03040207 (Carolina Coastal) and 03040206 (Waccamaw River). Within this watershed, the
United States Department of Agriculture Natural Resources Conservation Service (NRCS) has delineated
subwatershed areas with 14-digit HUC for the purpose of natural resource planning. The Town of
Calabash lies within the NRCS HUC 03040207020110 and 03040206090020. The beginning of the 14-
digit code uses the 8-digit designation of the USGS HUC.
URS subdivided these hydrologic units into drainage basins, using the most recent topographic mapping
provided by SBWSA. Figure 4-1 shows the drainage basins within the Town of Calabash and
surrounding areas.
4.3 HYDROLOGIC AND HYDRAULIC CHARACTERISTICS
4.3.1 Waterbodies
The Calabash River is the main water body in the Town of Calabash. Several small tributaries feed the
Calabash River in and around the Town of Calabash. According to NCDENR Division of Water Quality,
the Calabash River, from its source to the Intracoastal Waterway is considered SA waters. Any direct
tributaries are also considered SA waters. The SA classification denotes surface waters which are suitable
for commercial shellfishing and all other tidal saltwater uses.
4.3.2 Soils
The soils found in the Town of Calabash can be geographically organized into two groups. The area of
Calabash south of Highway 179 is predominately comprised of Blanton fine sand. This soil is moderately
well drained with a slow rate of surface runoff. Permeability is rapid in the sandy surface and subsurface
layers and moderate in the loamy subsoil. In this area, inclusions of Leon fine sand are also found east of
River Road. This soil also has a rapid permeability rate in the surface layer and a rapid to moderate rate
in the subsoil. The sandy construct of these soils is not an ideal soil for detention ponds or embankments,
but does introduce the potential of pervious concrete as a method to control stormwater runoff. This topic
is discussed further in Appendix A. (Figure 4-2)
The portion of Town north of Highway 179 is comprised of a variety of soils. The soils included in this
group are Baymeade fine sand, Foreston loamy fine sand, Goldsboro fine sandy loam, Leon fine sand,
Mandarin fine sand, Murville mucky fine sand, Pantego mucky loam, Rains fine sandy loam, and
Torhunta mucky fine sandy loam. The majority of these soils are not considered suitable linings for
1 02/27/02 4-1

' CHAPTER FOUR TOWN OF CALABASH
TOWN OVERVIEW STORMWATER QUANTITY MANAGEMENT PLAN
L'
I
1
detention ponds due to their sandy compositions. They are not considered suitable for embankments or
drainage ways because the soils are typically hard to pack and experience piping and caving along
waterways. Due to the composition and variety of soils present in the Calabash area, it is recommended
that soil borings be completed as part of the design for any stormwater BMP (i.e. retention basin, etc.).
Table 4-1 describes the soil types found in the Town of Calabash (USDA, 1986).
TABLE 4-1
TOWN OF CALABASH
SOILS DATA
Soil Type
Soil Name
Limitations for
Sanitary
High Water.
Hydric
Symbol
Pond Reservoir
Facilities Rating
Table Depth
Condition
Areas
(feet)
BaB
Baymeade
Severe: seepage.
Severe: poor filter.
4.0 — 5.0
No
fine sand
BnB
Blanton fine
Severe: seepage.
Moderate: wetness.
5.0 - 6.0
No
sand
BO
Bohicket
Slight. Slow
Severe: flooding,
+ 3.0-0.0
Yes
silty clayey
permeability.
ponding, peres
loam
slowly.
FO
Foreston
Severe: seepage.
Severe: wetness.
2.5-3.5
No
loamy fine
sand
GoA
Goldsboro
Moderate: seepage.
Severe: wetness.
2.0-3.0
No
fine sandy
loam
KrB
Kureb fine
Severe: seepage.
Severe: poor filter.
> 6.0
No
sand
Lo
Leon fine
Severe: seepage.
Severe: wetness,
0.0 - 1.0
Yes
sand
poor filter.
Ma
Mandarin
Severe: seepage.
Severe: wetness.
1.5 - 3.5
No
fine sand
Mk
Muckalee
Moderate: seepage.
Severe: flooding,
0.5-1.5
Yes
loam
wetness.
Mu
Murville
Severe: seepage.
Severe: ponding,
0.0 - 1.0
Yes
mucky fine
poor filter.
sand
Pn
Pantego
Moderate: seepage.
Severe: wetness.
0.0 - 1.5
Yes
mucky loam
Ra
Rains fine
Moderate: seepage.
Severe: wetness.
0.0 - 1.0
Yes
sandy loam
To
Torhunta
Severe: seepage.
Severe: wetness,
0.5-1.5
Yes
mucky fine
poor filter.
sandy loam
WaB
Wando fine
Severe: seepage.
Severe: poor filter.
4.0 - 6.0
No
sand
1 02/27/02 4-2

7
U
F
CHAPTER FOUR TOWN OF CALABASH
TOWN OVERVIEW STORMWATER QUANTITY MANAGEMENT PLAN
4.4 LAND USE
Land use within the Town primarily consists of residential and commercial development. Residential and
commercial properties are predominantly comprised of impervious surfaces as a result of paved areas
(e.g., roads, streets, parking lots, driveways, etc.) and structures (e.g., shopping centers, commercial
buildings, houses, barns, etc.). Vegetation, if present, varies and includes maintained lawns, maintained
scrub areas along utility easements, and landscaped areas.
4.5 EFFECTS ON WATER QUANTITY
The Town's drainage system presently consists of a network of ditches and swales with several catch
basins and piped outfalls to the Calabash River. Stormwater runoff quantity problems occur in various
locations across Calabash. These problems include:
• flooding
• soil erosion
• freshwater flow increase to estuaries/shellfish harvest areas
• clogged pipes, culverts, and ditches caused by debris from flooded areas
Development typically causes an increase in the volume and velocity of stormwater runoff that can result
in environmental hazards. Increased impervious surfaces reduce the opportunity for stormwater runoff to
be naturally retained and filtered by vegetation, wetlands, and estuaries. Pipe culverts located under roads
allow a ditch or channel to flow under the road. Culverts located under driveways allow ditches to flow
under the driveway.
Major flooding problems observed in Calabash, further discussed in Chapter Five, are a direct result of
the inadequate size, number, and/or location of stormwater inlets and detention devices, plus a lack of
vegetated ditches to accommodate the increased stormwater runoff from the development of impervious
surfaces. Stormwater management will allow the Town to effectively design, implement, construct, and
manage stormwater controls to prevent problems associated with the increased stormwater quantity.
1
02/27/02 4-3

CHAPTER FIVE
DRAINAGE PROBLEM AREA TOWN OF CALABASH
RECOMMENDATIONS STORMWATER QUANTITY MANAGEMENT PLAN
5.1 SELECTION CRITERIA
During the development of recommendations for each area of concern, several criteria were evaluated to
determine the most appropriate BMP for each area. The criteria which were evaluated were:
• Cost to implement and maintain
• Regulatory requirements
• Effectiveness at solving the problem
• Acceptability to the Town and the public
• Reliability
• Implementability
• Environmental Impact
• Commitment to longevity
Cost to implement and maintain
t The cost to implement and maintain each BMP was evaluated and compared. Specific costs for each
BMP were not determined, but relative costs of each BMP type were compared to determine the most cost
effective solutions.
' Regulatory Requirements
Each BMP was evaluated to determine if any special regulatory requirements would have to be met for
' implementation.
Effectiveness at solving the problem
' Each BMP was evaluated to determine the effectiveness at solving the flooding problem(s). The
recommended BMP may only alleviate the problem, not completely solve it, but the other criteria
indicated that this BMP was the most appropriate.
' Acceptability to the Town and the public
Each BMP was evaluated as to whether it would be an acceptable solution to the Town and to the public.
Education is an important aspect to acceptability of a BMP.
Reliability
The reliability over time of each BMP was evaluated. Some BMPs retain their effectiveness longer than
' others with a limited amount of maintenance.
Implementability
Some structural BMPs can not be constructed in certain areas due to regulatory and/or physical
constraints.
' Environmentallmpact
Each BMP was evaluated to determine if any positive or negative environmental impacts would occur due
to implementation of the BMP.
' Commitment to Longevity
For this criterion, the amount of maintenance required was evaluated to assess whether a commitment will
and/or can be made in regards to long-term maintenance and upkeep of the BMP.
1.
1
02/27/02 5-1

ICI
' CHAPTER FIVE
DRAINAGE PROBLEM AREA TOWN OF CALABASH
RECOMMENDATIONS STORMWATER QUANTITY MANAGEMENT PLAN
' 5.2 EVALUATIONS AND RECOMMENDATIONS
' Flooding is the primary stormwater problem in the Town of Calabash. Below is an explanation of the
flooding areas of concern, and recommendations for improvements. Deficiencies and recommendations
are summarized in Table 5-1.
' Persimmon Road (Near Calabash East)
Flooding problems in this area appear to be due to overgrown drainage channels and ineffective culvert
' pipes. Due to the crushed pipe under Persimmon Road (See pictures 1-4, Appendix B), storm flows back
up on the east side of Persimmon Road causing safety hazards for people and potentially for motorists if
and when the water floods the road.
Based upon available mapping, the stormwater in these channels is from portions of Village Green,
Calabash East, and possibly the Southern section of Hunters Trace. The stormwater should flow north
' through the roadside swales on Persimmon Road and then flow west in the channel through Calabash
East. Once it flows out of Calabash East, the flow should continue south through the channel and pipe
network under Highway 179 and eventually out to the channel that flows into the Calabash River.
' Currently there are several blockages in these channels reducing and/or preventing the flow of
stormwater.
Several actions should be taken to remedy the flooding and drainage problems in this area. The first
' action is to clean the drainage channels of larger plants and saplings and other blockages. These restrict
the flow during storm events. Next the pipe under Persimmon Road (near Anthony Clemmon's house)
should be replaced. If additional flow from Village Green is routed through this portion of the drainage
' system (See Village Green discussion below), the culvert may need to be enlarged. Based upon
preliminary stormwater quantity calculations using runoff coefficients and Q25 (peak discharge from a
25-year storm), the pipe size should be approximately 18 inches.
It is also recommended that the depressions behind the BB&T bank on Highway 179 (appear to be old
retention ponds) be redesigned to function properly and the pipe behind the BB&T bank be rerouted to
outfall into the retention ponds. Using the retention basins will help ease the problems in the channel
behind Ella's Restaurant (see description of this focus area later in this Chapter).
SBWSA is also looking into methods to improve water quality in this area, and these retention basins
' could possibly serve that purpose. The Town of Calabash should work with SBWSA to maximize the use
of these retention basins.
' A survey of the complete drainage system in this area is necessary to determine if the channels need to be
regraded to allow the stormwater to flow through the system. To ensure sufficient channel and pipe size, a
detailed survey which includes channel bottom, pipe inverts, and related information is necessary. This
I
data would then be used to complete some simple modeling and calculations to confirm the initial
assumptions.
' URS also recommends that the Town attempt to obtain a drainage easement for the channel that flows
west through Calabash East, and the channel that flows south to Highway 179 and on to the Calabash
River. An easement allows the Town to have maintenance access to the channel and culverts to help
1
02/27/02 5-2

U
' CHAPTER FIVE
DRAINAGE PROBLEM AREA TOWN OF CALABASH
RECOMMENDATIONS STORMWATER QUANTITY MANAGEMENT PLAN
' maintain stormwater flows. If SBWSA improves part of the system for water quality purposes, the
drainage easement could be obtained by SBWSA, thus easing the burden on the Town.
' Any drainage improvements which are recommended within the right-of-way an NCDOT roadway must
be coordinated with NCDOT. All plans and designs must be approved by NCDOT prior to
' implementation. It may be possible to obtain assistance from NCDOT on the construction of the system.
URS recommends that the Town have a meeting with NCDOT to discuss the drainage issues and how the
NCDOT and the Town can work together to alleviate the flooding problems.
To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system,
URS recommends that the Town encourage its residents to reduce the amount of impervious surface on
' their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas,
instead of directly off their property and into the street. As SBWSA further evaluates it's stormwater fee
structure, it will be looking to set a utility credit program for residents that go beyond the stormwater
' ordinance requirements to try to reduce and/or eliminate stormwater runoff from their lots.
Saltaire Village
Flooding problems in this area of Saltaire village appear to be due to an improperly located culvert pipe
and improper grading of the drainage channels (See pictures 7-9, Appendix B). The channel along the
northeast side of Saltaire village (coming from the northern pond at the entrance to Saltaire Village) is
also severely eroded and undercut.
rBased upon available mapping, the stormwater in these channels is mainly from Saltaire Village, though
the channel that flows along the west and north side of Saltaire Village begins south of Saltaire Village in
Carolina Shores. Therefore, a significant amount of land drains to this main channel. The stormwater
should flow through Saltaire Village, out to the perimeter channels, and north into Carolina Shores. The
outlet channel from the Saltaire Village culvert pipe is too wide and too deep, and is therefore acting as a
retention pond, creating backups into the pipe and flooding of Saltaire Village.
' Several actions should be taken to remedy the flooding and drainage problems in this area. The existing
' culvert pipe needs to be raised and enlarged to accommodate the flows and the base elevations of the
channels that need to be maintained. The area at the base of the Saltaire Village culvert should be re-
graded to prevent standing water. Based upon preliminary stormwater quantity calculations using runoff
coefficients and Q25 (peak discharge from a 25-year storm), the culvert pipe needs to be approximately
' 24 inches. Additionally, the channel from the northern pond at the Saltaire Village entrance needs to be
reshaped and re -graded to prevent erosion of the channel (which leads to sedimentation and blockages
downstream). Since the Town has no control over the stormwater once it flows north from Saltaire
' Village, flow control devices (check dams) may be able to be installed in the channels to slow the flow,
permit infiltration, and assist in reducing downstream flooding problems.
' A survey of the complete drainage system in this area is necessary to determine if the channel needs to be
regraded to allow the stormwater to flow through the system. To ensure sufficient channel and pipe size,
a detailed survey which includes channel bottom, pipe inverts, and related information is necessary. This
data would then be used to complete some simple modeling and calculations to confirm the initial
' assumptions.
1 02/27/02 . 5-3

L-1
CHAPTER FIVE
DRAINAGE PROBLEM AREA TOWN OF CALABASH
RECOMMENDATIONS STORMWATER QUANTITY MANAGEMENT PLAN
URS also recommends that the Town obtain a drainage easement for the drainage ways in and around
Saltaire Village. An easement allows the Town to have maintenance access to the channel and culverts to
' help maintain stormwater flows.
To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system,
' URS recommends that the Town encourage its residents to reduce the amount of impervious surface on
their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas,
instead of directly off their property and into the street. As SBWSA further evaluates it's stormwater fee
' structure, it will be looking to set a utility credit program for residents that go beyond the stormwater
ordinance requirements to try to reduce and/or eliminate stormwater runoff from their lots.
Hunter's Trace
The poor drainage system in this area causes flooding along Harbor Drive, south to Thomasboro Road.
The roadside swales are ineffective and in most places, non-existent. The drainage channels which were
meant to direct the stormwater flows out of Hunters Trace are overgrown and ineffective (See pictures 10-
13, Appendix B). The culvert pipe under Harbor Drive (at 1081 Harbor Drive) has been partially crushed
at the outfall, hampering flow of stormwater through the culvert and channel. Drain tile placed in swale
by property owner is ineffective, and may be making the drainage worse.
Based upon available mapping, the stormwater in these channels is from the southern section of Hunters
Trace. The stormwater should flow from Hunters Trace to the channels on either the east or west side of
the subdivision. These channels then flow north and eventually flow into Persimmon Swamp, just east of
Persimmon Road. Currently there are several blockages in these channels reducing and/or preventing the
flow of stormwater.
' Several actions should be taken to remedy the flooding and drainage problems in this area. The first
action is to improve the roadside swales along Harbor Drive and clean the drainage channels of larger
' plants and saplings. The excessive vegetation restricts the flow during storm events. Next the pipe under
Harbor Drive should be replaced, with proper roadside swales, the culvert pipe should be of sufficient size
to handle the flow. Based upon preliminary stormwater quantity calculations using runoff coefficients
and Q25 (peak discharge from a 25-year storm), the pipe should be approximately 18 inches.
Improving (and in places developing) roadside swales along Hunters Trace will also help alleviate the
some of the flooding problems along Thomasboro Road. The swales on Thomasboro road also need to be
' improved. Proper design of these roadside swales will help alleviate the flooding problems on this road.
A survey of the complete drainage system in this area is necessary to determine if the channel grading is
' appropriate to allow the stormwater to flow through the system and to determine the most appropriate
way to route the stormwater through the system. To ensure sufficient channel and pipe size, a detailed
survey which includes channel bottom, pipe inverts, and related information is necessary. This data
would then be used to complete simple modeling and calculations to confirm the initial assumptions.
URS also recommends that the Town attempt to obtain a drainage easement for the channel that flows
west from Harbor Drive, along with the channel that flows north along the western side of Hunters Trace.
An easement allows the Town to have maintenance access to the channel and culverts to help maintain
stormwater flows.
1
02/27/02 5-4

1
1
fi
CHAPTER FIVE
DRAINAGE PROBLEM AREA TOWN OF CALABASH
RECOMMENDATIONS STORMWATER QUANTITY MANAGEMENT PLAN
To help ease quantity problems further down the system, near Persimmon Swamp, a retention basin on
the Town property along Persimmon Road (west of Hunters Trace) is recommended. This basin should
be designed to handle the flows from Hunters Trace, as well as from portions of Thomasboro Road, if it is
determined (through survey) that these flow can be routed in this direction. Some flows from Persimmon
Road could potentially be routed to this retention pond, thus easing some problems in Saltaire Village.
Any drainage improvements which are recommended within the right-of-way an NCDOT roadway must
be coordinated with NCDOT. All plans and designs must be approved by NCDOT prior to
implementation. It may be possible to obtain assistance from NCDOT on the construction of the system.
URS recommends that the Town have a meeting with NCDOT to discuss the drainage issues and how the
NCDOT and the Town can work together to alleviate the flooding problems.
To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system,
URS recommends that the Town encourage its residents to reduce the amount of impervious surface on
their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas,
instead of directly off their property and into the street. As SBWSA further evaluates it's stormwater fee
structure, it will be looking to set a utility credit program for residents that go beyond the stormwater
ordinance requirements to try to reduce and/or eliminate stormwater runoff from their lots.
Village Green
The poor drainage system in this area causes flooding throughout Village Green. The roadside swales are
ineffective and in most places, non-existent. The drainage channel on the north side of the subdivision
which were meant to direct the stormwater flows out of Village Green are overgrown and ineffective (See
pictures 14-16, Appendix B).
Based upon available mapping, the stormwater should flow from Village Green to the channels on either
the north or west side of the subdivision. These channels then flow north and eventually flow into
Persimmon Swamp, just east of Persimmon Road. Currently there are several blockages in these channels
reducing and/or preventing the flow of stormwater.
Several actions should be taken to remedy the flooding and drainage problems in this area. The first
action is to improve the roadside swales throughout Village Green and clean the drainage channels of
larger plants and saplings. The excessive vegetation restricts the flow during storm events. With the
improved roadside swales the new pipe that was installed by the Town in 2001, should be enlarged to a
15 inch pipe.
A survey of the complete drainage system in this area is necessary to determine if the channel grading is
appropriate to allow - the stormwater to flow through the system and to determine the most appropriate
way to route the stormwater through the system. To ensure sufficient channel and pipe size, a detailed
survey which includes channel .bottom, pipe inverts, and related information is necessary. This data
would then be used to complete simple modeling and calculations to confirm the initial assumptions.
URS also recommends that the Town attempt to obtain a drainage easement for the channel that flows
north from Village Green. An easement allows the Town to have maintenance access to the channel and
to help maintain stormwater flows.
02/27/02 5-5

CHAPTER FIVE
DRAINAGE PROBLEM AREA TOWN OF CALABASH
RECOMMENDATIONS STORMWATER QUANTITY MANAGEMENT PLAN
To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system,
URS recommends that the Town encourage its residents to reduce the amount of impervious surface on
' their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas,
instead of directly off their property and into the street. As SBWSA further evaluates it's stormwater fee
structure, it will be looking to set a utility credit program for residents that go beyond the stormwater
' ordinance requirements to try to reduce and/or eliminate stormwater runoff from their lots.
Putt Putt Golf
The flooding problems at the Putt Putt Golf on Highway 179 were the result of the backup of the storm
drain system along Highway 179 (See picture 17, Appendix B). NCDOT has completed some
improvements at an outfall on the opposite side of the road, which are believed to have solved the
flooding problem at the Putt Putt. URS was unable to reach the owners of the business to confirm that the
problem has been solved.
Ella's Restaurant
The channel behind Ella's Restaurant begins near the BB&T bank on Highway 179 and flows down to the
Calabash River. This channel is a blue line stream, therefore any modifications to the channel require the
approval of the NCDENR Division of Water Quality.
' It is recommended that the pipe which is located in the channel downstream from Ella's Restaurant be
removed and the flow returned to an open channel. Additionally, the channel dimensions should be
' evaluated so the channel can be improved to handle the flows without excessive sedimentation.
Sedimentation reduces channel capacity, thus causing backups and potential flooding. As mentioned
above, the improvements to this channel must be approved by NCDENR Division of Water Quality prior
' to any work being initiated.
To ensure sufficient channel and pipe size, a detailed survey which includes channel bottom, pipe inverts,
and related information is necessary. This data would then be used to complete simple modeling and
calculations to confirm the initial assumptions.
To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system,
URS recommends that the Town encourage its residents to reduce the amount of impervious surface on
their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas,
instead of directly off their property and into the street. As SBWSA further evaluates it's stormwater fee
' structure, it will be looking to set a utility credit program for residents that go beyond the stormwater
ordinance requirements to try to reduce and/or eliminate stormwater runoff from their lots.
' Sommersett and Oak Drive/Callahans/Riverview Drive
These areas are experiencing drainage and flooding problems, and are being addressed here together,
since they are all interrelated problems (See pictures 18-23, Appendix B). The stormwater flows in this
basin originate from near Highway 179 and'flow down River Drive and Riverview Drive and eventually
end up in the Calabash River. Additionally, there is stormwater that originated from the other side of
Highway 179 that ends up in this basin by flowing through culverts under Highway 179.
' The stormwater flows are poorly directed and are allowed to sheet flow across most of the area. Roadside
swales are present along River Road and Riverview Drive to direct flows in these areas. Excessive
stormwater flows across the properties between these two roads has caused problems in the past.
1
02/27/02 5-6

' CHAPTER FIVE
DRAINAGE PROBLEM AREA
RECOMMENDATIONS
TOWN OF CALABASH
STORMWATER QUANTITY MANAGEMENT PLAN
Additionally, some property behind Callahans is being considered for further development and the Town
does not want this to adversely impact the stormwater system.
It is recommended that a retention basin be installed on the property behind Callahans. This can be
landscaped to fit in with the development, and actually be a drawing point for pedestrians. Flows from
River Road, and even possibly Riverview Drive could be routed to this location. The outfall for the
retention basin should be directed down to the existing channel between Sommersett and Oak Drive. This
channel should be shaped and landscaped to provide better infiltration. Additionally, the upper pipe
should be removed and the culverts emptying into this channel should be redesigned to reduce erosion at
the inlet to the channel. If, due to property constraints a retention basin is not possible behind Callahans,
this area (between Sommersett and Oak Drive) could be redesigned as a retention basin.
These retention basins could also serve as water quality BMPs, and thus the Town may be able to work
with SBWSA on the design and installation. At this time URS is under contract with the SBWSA to
study this area for locating a water quality BMP. URS, along with other SBWSA contractors, have been
evaluating this area in regards to runoff quantities and drainage patterns. Preliminary studies for sizing
and location of a stormwater BMP, such as a retention basin, have been initiated.
A survey of the complete drainage system in this area is necessary to determine if the channel grading is
appropriate to allow the stormwater to flow through the system and to determine the most appropriate
way to route the stormwater through the system. To ensure sufficient channel and pipe size, a detailed
survey which includes channel bottom, pipe inverts, and related information is necessary. This data
would then be used to complete simple modeling and calculations to confirm the initial assumptions.
URS also recommends that the Town attempt to obtain a drainage easement for any channels that direct
flow to the retention basin, along with the channel that flows out from the retention basin and down
toward the Calabash River. An easement allows the Town to have maintenance access to the channel and
to help maintain stormwater flows.
To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system,
URS recommends that the Town encourage its residents to reduce the amount of impervious surface on
their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas,
instead of directly off their property and into the street. As SBWSA further evaluates it's stormwater fee
structure, it will be looking to set a utility credit program for residents that go beyond the stormwater
ordinance requirements to try to reduce and/or eliminate stormwater runoff from their lots.
5.3 OPERATION AND MAINTENANCE
During the field inspection of the system, several inlets were covered with dirt and debris and many of the
roadside swales were blocked and/or filled. Most of the inlets and pipe systems are in need of
maintenance and pumping to remove sand buildup.
Calabash should work with SBWSA when developing a maintenance program for the storm drain system
' so as to not overlap duties and to ensure effective and efficient operation and maintenance of the system.
Additionally, all storm drain inlets should be inspected and cleaned at least once a year, and/or after each
major storm. Prior to implementation of any of the above actions, an inspection of the existing system, to
1 02/27/02 5-7

CHAPTER FIVE
DRAINAGE PROBLEM AREA TOWN OF CALABASH
RECOMMENDATIONS STORMWATER QUANTITY MANAGEMENT PLAN
include determining the length of all pipes, should be completed. This will determine if any of the
existing system can be used in conjunction with new systems.
Once developed, use of SBWSA's inventory system for future maintenance tracking will be very useful.
Regular monitoring and maintenance of all components of the storm drain system is recommended to
prevent problems.
Roadside swales should be periodically cleaned of debris and mowed. Vegetation is critical for
infiltration and pollutant removal, but excessive vegetation will block flow.
Table 5-1
Recommendations
Calabash
Location
Problem Description'
Recommended Action
Persimmon Road
Crushed culvert/ blocked
Improve channels, replace culvert,
channels
redesign retention basins behind
BB&T
Saltaire Village
Improper grading and channel
Replace culvert, regrade channels,
dimension; Improper culvert
place check dams in channels
placement/size
Hunters Trace
Degraded/non-existent roadside
Improve roadside swales and
swales; Damaged culverts;
channels, replace culvert, install
overgrown, poorly graded
retention basin
channels
Village Green
Poor roadside Swale system and
Improve roadside swales and
channels draining Village Green
channels
Putt Putt Golf
Flow backs up into pond from
No Action at this time
Highway 179 drainage.
Channel behind Ellas
Channel full of debris and
Remove pipes and restore channel
inappropriately sized pipes.
to natural conditions
Drainage between Sommersett
Improve drainage to this area
Improve channel, remove upper
and Oak Drive
from northern portion of basin
pipe and redesign drainage into
channel. Possibly install retention
basin, if determined that
Callahans location is not
appropriate.
Callahans
Poor drainage in the area and
Install retention basin behind
down to Calabash River
Callahans, create drainage swales
to direct stormwater flows
Riverview Drive
Sedimentation and flooding near
Improvements in the upstream
end of road.
portion of the basin should
improve this area
02/27/02 5-8

' CHAPTER SIX
STORMWATER MANAGEMENT TOWN OF CALABASH
PROGRAM STORMWATER QUANTITY MANAGEMENT PLAN
The recommendations presented in Chapter Five are summarized in this Chapter. Some of the
P P
recommendations should be implemented as Capital Improvement Program (CIP) projects which are
' prioritized using the criteria described in Section 6.2. Recommendations for minor repair and
maintenance should be made part of the Town's operating budget. Recommended policy changes may or
may not have budget implications.
' 6.1 RECOMMENDATION SUMMARY
The project rankings are shown in Table 6-1. Costs for the recommendations (design and construction)
were estimated (order of magnitude) and are shown in Table 6-2. It should be noted that these are only
estimates. Surveying and Hydraulic & Hydrologic modeling are necessary to determine more precise
estimates on sizes of facilities, length of pipe, etc. The costs of obtaining drainage easements and whether
the Town can obtain land needed for several of the projects is also a factor (drainage easement cost and
other land costs are not included in the estimates). Therefore, these costs should only be looked at as
order of magnitude given the recommendations presented in Chapter Five.
6.2 PROJECT SELECTION CRITERIA
' The project selection criteria were used to evaluate which recommended projects are the most crucial and
should be implemented first in the Capital Improvement Program. The following criteria were used:
• Safety
• Quantity Benefits
• Quality Benefits
' Sa e
This criterion is for projects that maintain safe travelways during rain storms and protect against property
damage from flooding. The safety benefits are apparent from the nature of the project.
Quantity Benefits
Problems that are caused by increased runoff volumes and peak discharges include sedimentation of
estuaries and storm drain system components, increased maintenance, erosion and flooding problems.
Quantity problems may be due to existing development or potential problems due to planned
development may be averted with recommended projects.
Quality Benefcts
Though these projects are mainly water quantity control projects, water quantity in the receiving
waterbodies cannot be degraded due to the stormwater discharge. The amount of water quality benefits
are not easily determined for each project. Problems caused by poor water quality include increased
sediment loading, algae blooms caused by excess pollutants in the runoff, loss of plant life due to
pollutants, and loss of fishing, shellfishing, and other recreation due to pollutants. Projects which
improve the quality of stormwater runoff will help protect and improve the quality of water in the
Calabash River.
Table 6-1 lists the project selection criteria as well as the rankings of each proposed project.
1 02/27/02 6-1

CHAPTER SIX
STORMWATER MANAGEMENT TOWN OF CALABASH
PROGRAM STORMWATER QUANTITY MANAGEMENT PLAN
Table 6-1
Project Selection Criteria and Ranking
Calabash
Persimmon
Improve channels,
Road
Flooding
4
4
1
2
replace culvert, redesign
retention basins behind
BB&T
Saltaire
Replace culvert, regrade
Village
Flooding
2
2
6
3
channels, place check
dams in channels
Hunters
Improve roadside swales
Trace
Flooding
1
1
5
1
and channels, replace
culvert, install retention
basin
Village
Improve roadside swales
Green
Flooding
3
3
7
5
and channels
Channel
Remove pipes and
behind Ellas
Flooding
7
7
3
7
restore channel to
natural conditions
Drainage
Improve channel,
between
Flooding
6
6
4
6
remove upper pipe and
Sommersett
redesign drainage into
and Oak
channel. Possibly install
Drive
retention basin, if
determined that
Callahans location is not
appropriate.
Callahans
Install retention basin
Flooding
5
5
2
4
behind Callahans, create
drainage swales to direct
stormwater flows
Riverview
Improvements in the
Drive
Flooding
--
--
--
--
upstream portion of the
basin should improve
this area
Ranking: 1=highest; 7=lowest.
6.3 CAPITAL IMPROVEMENT PROGRAM
Inadequate system capacity is the biggest water quantity problem requiring capital improvements. Table
6-1 describes the capital improvement actions that have been recommended, and the recommended order
02127/02 6-2

CHAPTER SIX
STORMWATER MANAGEMENT TOWN OF CALABASH
PROGRAM STORMWATER QUANTITY MANAGEMENT PLAN
' of project implementation. The implementation priority was determined based upon the ranking of the
project with regard to the project evaluation criteria described in Section 6.2.
Surveying and modeling of the area is considered a top priority in order to determine the size and amount
of improvements that need to be done to fix problem flooding areas. Stormwater modeling is briefly
described below.
Water Quantity Modeling
Stormwater quantity is modeled to predict flooding problems and analyze drainage system capacity and
hydraulic performance. A detailed hydrologic and hydraulic computer model is suited for the analysis of
a large drainage area that links runoff hydrographs from smaller subdrainage areas. Simpler models are
' available to use for specific design calculations such as culverts, drop inlets, site drainage systems, etc.
The estimated costs for the action items are preliminary, order of magnitude costs. The scheduling of
these action items is dependent upon the Town's financing needs and methods. Funding options are
described in Section 6.5.
6.4 OPERATION AND MAINTENANCE PROGRAM
A planned program of storm drain inspections, and minor cleaning, a planned program of ditch cleaning,
and a planned program of infiltration system inspection should be implemented jointly with SBWSA. A
work order process and form should be developed to track work progress and to record maintenance work
for overall program success.
Maintenance costs will be dependent on the length of pipe, length of roadside swales, number of drop
inlets, and size of infiltration facilities. A few estimates for maintenance costs are approximately $1.00
per linear foot for cleaning ditches and pipes (assuming Town personnel and equipment), approximately
$40-$75 per inlet for cleaning (depending on size), and approximately $1,000 per year to clean each
infiltration facility (each facility will vary with size and type). The Town should also investigate the use
of the spoil areas used by the Corps of Engineers for dredge spoils as a place to dispose of sediment from
the pipes and inlets. This action would require permitting.
6.5 FUNDING
' The amount necessary to fund these projects can come from several sources. The costs estimated for the
action items are preliminary, order of magnitude amounts.
Taxes
The Town could raise property taxes to fund part or all of the program. The public usually does not
respond well to this option. A dedicated millage would require a referendum, which may be difficult to
' sell to the public. A dedicated millage would mean that the Town could depend on a certain amount year
to year being committed to a planned program of operation and maintenance (O & M) and replacement
and improvements.
02/27/02 6-3

I
CHAPTER SIX
STORMWATER MANAGEMENT TOWN OF CALABASH
PROGRAM STORMWATER QUANTITY MANAGEMENT PLAN
Grants and Loans
There are several sources that the Town can apply to for grants and low interest loans. Due to the
location of the Town, and its sensitive environment, the Town should have a good chance at receiving a
variety of grants. Some of these programs include:
• Clean Water Management Trust Fund
• Clean Water Act Section 319 Grants
• Small Watershed Program Grants
• State Construction Grants and Loans
These possible sources of additional funding will need to be evaluated by the Town to establish policy on
additional funding methods.
Table 6-2
Capital Improvement Program
Calabash
Location
Action Description
Estimated Cost
Persimmon Road
Improve channels, replace
$200,000
culvert, redesign retention
basins behind BB&T
Saltaire Village
Replace culvert, regrade
$40,000
channels, place check
dams in channels
Hunters Trace
Improve roadside swales
$100,000
and channels, replace
culvert, install retention
basin
Village Green
Improve roadside swales
$50,000
and channels
Channel behind Ella's
Remove pipes and restore
$100,000
channel to natural
conditions
Drainage between Sommersett
Improve channel, remove
$30,000 (retention basin not
and Oak Drive
upper pipe and redesign
included)
drainage into channel.
Possibly install retention
basin, if determined that
Callahans location is not
a ro riate.
Callahans
Install retention basin
$100,000
behind Callahans, create
drainage swales to direct
stormwater flows
1 02/27/02 6-4

I
1
Il
u
L
CHAPTER SEVEN TOWN OF CALABASH
REFERENCES STORMWATER QUANTITY MANAGEMENT PLAN
Arnold, J.A., ed., D.E. Line, S.W. Coffey, and J. Spooner. 1993. Stormwater Management
Guidance Manual. North Carolina Cooperative Extension Service and North Carolina
Division of Environmental Management. Raleigh, NC.
Center for Watershed Protection and Land Ethics, Inc. Blueprint to Protect Coastal Water Quality. A
Guide to Successful Growth Management in the Coastal Region of North Carolina, Prepared for
the Neuse River Council of Governments and the North Carolina Division of Environmental
Management.
Environmental Protection Agency.
1995. Watershed Protection: A Project Focus. Washington, DC: Office of Wetlands, Oceans,
and Watersheds.
l 997a. Designing an Information Management System for Watersheds. Washington, DC: Office
of Wetlands, Oceans, and Watersheds, Office of Wastewater Management and Office of Water.
1997b. Top 10 Watershed Lessons Learned. EPA 840-F-97-001. Washington, DC: Office of
Water and Office of Wetlands, Oceans, and Watersheds.
North Carolina Department of Environment and Natural Resources.
1998. Basinwide Assessment Report — Lumber River Basin. Environmental Sciences Branch.
1999. Lumber River Basinwide Water Quality Plan. Raleigh, NC: Division of Environmental
Management.
A Guide to Protecting Coastal Resources Through the CAMA Permit Program. Raleigh, NC:
Division of Coastal Management.
Town of Calabash. 1994. CAMA Land Use Plan Update.
Ogden Environmental and Engineering Services, Inc. 1994. City of Charlotte Storm Water Services
Credit Application Instruction Manual. Charlotte, NC: City of Charlotte Stormwater Services.
US Department of Agriculture. 1986. Soil Survey of Brunswick County, North Carolina. Soil
Conservation Service.
1 02/27/02 7-1

== m m r== = r am= m r m m = = = m

�—_—Ra
Ra Ra
}
s
Ly Ra
Ly
Ly
C'QA tl6 GoA / Go
tk I
Ma
On GoA
NMk Ra
a . Mu
_� y
Lo
o Lo i Goy Ly Ly Ra.
... �
GoA
Mu
�r Ly 1 A Pn L> To
Pn
Ra To Lo
Ly
o B 18 % LO Ma Mu / % Baf3
Ma ' t
O _ tv J — o
KrS Lo Ma ( ��
BaB u KA
to ` •T.; ` 1 uz l � 1u y
7m r
SaB
K.R Muu Lo BrtB
a ash �
e
• 4nB KrB �, a8 i3iiB
Ma tAa x xl O Crct k
a
8n8
i *�Mk rt f l� '" Forest
#f K rEl ,
so o-U,
BO3f
• -. 7 � �' K r B
Lo COLKINS
* ` 91,
NECK
Bne PaA
Mk u
LEGEND \ TOWN OF CALABASH
STORMWATER QUANTITY MANAGEMENT
Town Limits PLAN
BaB Baymeade fine sand Ma Mandarin fine sand SOIL MAP
BnB Blanton fine sand Mk Muckalee loam
BO Bohicket silty clay loam MU Murviile mucky fine sand FIGURE 4-2
Fo Foreston loamy fine sand Pn Pantego mucky loam
GoA Goldsboro fine sandy loam Ra Rains fine sandy loam
KrB Kureb fine sand To Torhunta mucky fine sandy loam URS
Lo Leon fine sand WaB Wando fine sand URS Corporation - North Carolina
3109 Poplarwood Court, Suite 301
Source: USDA, Sod Survey of Wunsv k County. 1986. Raleigh, NC 27604

E
APPENDIX A
PERVIOUS PAVEMENT
0

L
C " PO'
EPA
DESCRIPTION
United States Office of Water EPA 832-F-99-023
Environmental Protection Washington, D.C. September 1999
Agency
Storm Water
Technology Fact Sheet
Porous Pavement
Porous pavement is a special type of pavement that
allows rain and snowmelt to pass through it,
thereby reducing the runoff from a site and
surrounding areas. In addition, porous pavement
filters some pollutants from the runoff if
maintained.
There are two types of porous pavement: porous
asphalt and pervious concrete. Porous asphalt
pavement consists of an open -graded coarse
aggregate, bonded together by asphalt cement, with
sufficient interconnected voids to make it highly
permeable to water. Pervious concrete consists of
specially formulated mixtures of Portland cement,
uniform, open -graded coarse aggregate, and water.
Pervious concrete has enough void space to allow
rapid percolation of liquids through the pavement.
The porous pavement surface is typically placed
over a highly permeable layer of open -graded
gravel and crushed stone. The void spaces in the
aggregate layers act as a storage reservoir for
runoff. A filter fabric is placed beneath the gravel
and stone layers to screen out fine soil particles.
Figure 1 illustrates a common porous asphalt
pavement installation.
Two common modifications made in designing
porous pavement systems are (1) varying the
amount of storage in the stone reservoir beneath the
pavement and (2) adding perforated pipes near the
top of the reservoir to discharge excess storm water
after the reservoir has been filled.
Some municipalities have also added storm water
reservoirs (in addition to stone reservoirs) beneath
the pavement. These reservoirs should be designed
to accommodate runoff from a design storm and
should . provide for infiltration through the
underlying subsoil.
APPLICABILITY
Porous pavement may substitute for conventional
pavement on parking areas, areas with light traffic,
and the shoulders of airport taxiways a runways,
provided that the grades, subsoils, drainage
characteristics, and groundwater conditions are
suitable. Slopes should be flat or very gentle. Soils
should have field -verified permeability rates of
greater than 1.3 centimeters (0.5 inches) per hour,
and there should be a 1.2 meter (4-foot) minimum
clearance from the bottom of the system to bedrock
or the water table.
ADVANTAGES AND DISADVANTAGES
The advantages of using porous pavement include:
• Water treatment by pollutant removal.
• Less need for curbing and storm sewers.
• Improved road safety because of better skid
resistance.
• Recharge to local aquifers.
The use of porous pavement may be restricted in
cold regions, and regions or regions with high wind
erosion rates, and areas of sole -source aquifers.
The use of porous pavement is highly constrained,
requiring deep permeable soils, restricted traffic,
and adjacent land uses. Some specific

Berm Keeps Off -site Runoff Asphalt is Vacuum Swept,
and Sediment out. Provides Followed by Jet Hosing to
Temporary Stage Keep Pores Open S
overflow 4—_
Pipe - - -
Perforated Pipe Discharges
Only When 2-Year Storage
Volume Exceeded
Sign Posted to Prevent
Resurfacing and Use of
Abrasives, and to Restrict
Truck Paridng
P�ted
Finer Fabric Limes Sides
of Reservoir to Prevent —►
Sediment Entry Stone Reservoir trains in 48 - 72 Hours
'Ak
10*�'
Undisturbed Soils with a Field Capacity > 0.27 A�.
Inches/1-lour Preferably A.50 IncheslHour
Observation Well
Gravel Course or 6-
Inch Sand Layer
Source: Modified from MWCOG, 1987.
' FIGURE 1 TYPICAL POROUS PAVEMENT INSTALLATION
' disadvantages of porous pavement include the
following:
' Many pavement engineers and contractors
lack expertise with this technology.
• Porous pavement has a tendency to become
clogged if improperly installed or
maintained.
' • Porous pavement has a high rate of failure.
'0 There is some risk of contaminating
groundwater, depending on soil conditions
and aquifer susceptibility.
' • Fuel may leak from vehicles and toxic
chemicals may leach from asphalt and/or
' binder surface. Porous pavement systems
are not designed to treat these pollutants.
• Some building codes may not allow for its
installation.
• Anaerobic conditions may develop in
underlying soils if the soils are unable to
dry out between storm events. This may
impede microbiological decomposition.
As noted above, the use of porous pavement does
create risk of groundwater contamination.
Pollutants that are not easily trapped, adsorbed, or
reduced, such as nitrates and chlorides, may
continue to move through the soil profile and into
the groundwater, possibly contaminating drinking
water supplies. Therefore, until more scientific data
is available, it is not advisable to construct porous
pavement near groundwater drinking supplies.

1
n
In addition to these documented pros and cons of
porous pavements, several questions remain
regarding their use. These include:
• Whether porous pavement can maintain its
porosity over a long period of time,
particularly with resurfacing needs and
snow removal.
• Whether porous pavement remains capable
of removing pollutants after subfreezing
weather and snow removal.
• The cost of maintenance and rehabilitation
options for restoration of porosity:
DESIGN CRITERIA
Porous pavement - along with other infiltration
technologies like infiltration basins and trenches -
have demonstrated a short life span. Failures
generally have been attributed to poor design, poor
construction techniques, subsoils with low
permeability, and lack of adequate preventive
maintenance. Key design factors that can increase
the performance and reduce the risk of failure of
porous pavements (and other infiltration
technologies) include:
• Site conditions;
• Construction materials; and
•. Installation methods.
These factors are discussed further in Table 1.
PERFORMANCE
Porous pavement pollutant removal mechanisms
include absorption, straining, and microbiological
decomposition in the soil. An estimate of porous
pavement pollutant removal efficiency is provided
by two long-term monitoring studies conducted in
Rockville, MD, and Prince William, VA. These
studies indicate removal efficiencies of between 82
and 95 percent for sediment, 65 percent for total
phosphorus, and between 80 and 85 percent of total
nitrogen. The Rockville, MD, site also indicated
high removal rates for zinc, lead, and chemical
oxygen demand. Some key factors to increase
pollutant removal include:
• Routine vacuum sweeping and high
pressure washing (with proper disposal of
removed material).
• Drainage time of at least 24 hours.
• Highly permeable soils.
• Pretreatment of runoff from site.
• Organic matter in subsoils.
• Clean -washed aggregate.
Traditionally, porous pavement sites have had a
high failure rate - approximately 75 percent.
Failure has been attributed to poor design,
inadequate construction techniques, soils with low
permeability, heavy vehicular traffic, and
resurfacing with nonporous pavement materials.
Factors enhancing longevity include:
• Vacuum sweeping and high-pressure
washing.
• Use in low -intensity parking areas.
• Restrictions on use by heavy vehicles.
• Limited use of de-icing chemicals and sand.
• Resurfacing.
• Inspection and enforcement of
specifications during construction.
• Pretreatment of runoff from offsite.
• Implementation of a stringent sediment
control plan.
OPERATION AND MAINTENANCE
Porous pavements need to be maintained.
Maintenance should include vacuum sweeping at
least four times a year (with proper disposal of

ITABLE 1 DESIGN CRITERIA FOR POROUS PAVEMENTS
Design Criterion Guidelines
Site Evaluation
Take soil boring to a depth of at least 1.2 meters (4 feet) below bottom of stone
reservoir to check for soil permeability, porosity, depth of seasonally high water
'
table, and depth to bedrock.
•
Not recommended on slopes greater than 5 percent and best with slopes as flat
as possible.
•
Minimum infiltration rate 0.9 meters (3 feet) below bottom of stone reservoir. 1.3
centimeters (0.5 inches) per hour.
'
•
Minimum depth to bedrock and seasonally high water table: 1.2 meters (4 feet).
•
Minimum setback from water supply wells: 30 meters (100 feet).
'
•
Minimum setback from building foundations: 3 meters (10 feet) downgradient,
30 meters (100 feet) upgradient.
•
Not recommended in areas where wind erosion supplies significant amounts of
windblown sediment.
•
Drainage area should be less than 6.1 hectares (15 acres).
Traffic conditions
Use for low -volume automobile parking areas and lightly used access roads.
•
Avoid moderate to high traffic areas and significant truck traffic.
•
Avoid snow removal operations; post with signs to restrict the use of sand, salt,
and other deicing chemicals typically associated with snow cleaning activities.
'
Design Storm Storage Volume
Highly variable; depends upon regulatory requirements. Typically design for
storm water runoff volume produced in the tributary watershed by the 6-month,
24-hour duration storm event.
Drainage Time for Design Storm 0
Minimum: 12 hours.
•
Maximum: 72 hours.
Recommended: 24 hours.
'0
Construction 0
Excavate and grade with light equipment with tracks or oversized tires to prevent
soil compaction.
As needed, divert storm water runoff away from planned pavement area before
'0
and during construction.
•
A typical porous pavement cross-section consists of the following layers: 1)
porous asphalt course, 5-10 centimeters (2-4 inches) thick; 2) filter aggregate
course; 3) reservoir course of 4-8 centimeters (1.5-3-inch) diameter stone; and
4) filter fabric.
'0
Porous Pavement Placement
Paving temperature: 240° - 260° F.
Minimum temperature: 50° F.
air
•
Compact with one or two passes of a 10,000-kilogram (10-ton)roller.
'0
Prevent any vehicular traffic on pavement for at least two days.
Pretreatment 0
Pretreatment recommended to treat runoff from off -site areas. For example,
place a 7.6-meter (25-foot) wide vegetative filter strip around the perimeter of the
'
porous pavement where drainage flows onto the pavement surface.
Source: Field, 1982.

removed material), followed by high-pressure
hosing to free pores in the top layer from clogging.
Potholes and cracks can be filled with patching
mixes unless more than 10 percent of the surface
area needs repair. Spot -clogging may be fixed by
drilling 1.3 centimeter (half -inch) holes through the
porous pavement layer every few feet.
The pavement should be inspected several times
during the first few months following installation
and annually thereafter. Annual inspections should
take place after large storms, when puddles will
make any clogging obvious. The condition of
adjacent pretreatment devices should also be
inspected.
COSTS
The costs associated with developing a porous
pavement system are illustrated in Table 2.
Estimated costs for an average annual maintenance
program of a porous pavement parking lot are
approximately $4,942 per hectare per year ($200
per acre pdr year). This cost assumes four
inspections each year with appropriate jet hosing
and vacuum sweeping treatments.
REFERENCES
1.
2.
3.
4.
Field, R., et al., 1982. "An Overview of
Porous Pavement Research." Water
Resources Bulletin, Volume 18, No. 2, pp.
265-267.
Metropolitan Washington Council of
Governments, 1987. Controlling Urban
Runoff A Practical Manual for Planning
and Designing Urban BMPs.
Metropolitan Washington Council of
Governments, 1992. A Current Assessment
ofBestManagementPractices: Techniques
for Reducing Nonpoint Source Pollution in
a Coastal Zone.
Southeastern Wisconsin Regional Planning
Commission, 1991. Costs of Urban
Nonpoint Source Water Pollution Control
Measures, Technical Report No. 31.
5. U.S. EPA, 1981. Best Management
Practices Implementation Manual.
6. U.S. EPA, 1992. Stormwater Management
for Industrial Activities:. Developing
Pollution Prevention Plans and Best
Management Practices. EPA 833-R-92-
006.
7. Washington State Department of Ecology,
1992. Stormwater ManagementManualfor
the Puget Sound Basin.
ADDITIONAL INFORMATION
Andropogon Associates, Ltd.
Yaki Miodovnik
374 Shurs Lane
Philadelphia, PA 19128
Cahill Associates
Thomas H. Cahill
104 S. High Street
West Chester, PA 19382
Center for Watershed Protection
Tom Schueler
8391 Main Street
Ellicott City, MD 21043
Fairland Park, Maryland
Ken Pensyl
Nonpoint Source Program
Water Management Administration
Maryland Department of the Environment
2500 Broening Highway
Baltimore, MD 21224
Fort Necessity National Battlefield
National Park Service
1 Washington Parkway
Farmington, PA 15437
Massachusetts Highway Department
Clem Fung
Research and Materials Group
400 D Street
Boston, MA 02210

Morris Arboretum
Robert Anderson
9414 Meadowbrook Avenue
Philadelphia, PA 19118
Washington Department of Ecology
Linda Matlock
Stormwater Unit
P.O. Box 47696
Olympia, WA 98504-7696
The mention of trade names or commercial
products does not constitute endorsement or
recommendation for the use by the U.S.
Environmental Protection Agency.
For more information contact:
Municipal Technology Branch
U.S. EPA
Mail Code 4204
401 M St., S.W.
Washington, DC, 20460
oMTB
�ft�
MUNICIPAL TECHNOLOGY BRAN H

APPENDIX B
STORMWATER FOCUS AREA PICTURES
u
1

ij-
Photo 1
Description
Roadside ditch along
west side of Persimmon
Road across from
Clemmons residence.
View of southern portion
of ditch.
Drainage Concern
Vegetative debris in
channel may slow flow
during rainfall events.
Photo 2
Description
�:. West side of Persimmon
Road across from
y Y o
L Clemmons residence.
View of ditch
..�'y convergence.
Drainage Concern
Vegetative debris in
. channel may slow flow
during rainfall events.
Photo 3
Description
West side of Persimmon
Road across from
' Clemmons residence.
View of roadway culvert
iIAand ditch convergence.
Drainage Concern
Vegetative debris in
channel may slow flow
during rainfall events.
Culvert requires
maintenance.
Photo 1
Description
Roadside ditch along
west side of Persimmon
Road across from
Clemmons residence.
View of southern portion
of ditch.
Drainage Concern
Vegetative debris in
channel may slow flow
during rainfall events.
Photo 2
Description
�:. West side of Persimmon
Road across from
y Y o
L Clemmons residence.
View of ditch
..�'y convergence.
Drainage Concern
Vegetative debris in
. channel may slow flow
during rainfall events.
Photo 3
Description
West side of Persimmon
Road across from
' Clemmons residence.
View of roadway culvert
iIAand ditch convergence.
Drainage Concern
Vegetative debris in
channel may slow flow
during rainfall events.
Culvert requires
maintenance.

Photo 4
ON
*�4
xj�,
Description
�! West side of Persimmon
Road in front of
k Clemmons residence.
IS
View of roadway culvert.
ZOO
"Azar� �'a�;''f �;6"`,Vrra�i �y/� ► r Drainage Concern
Vegetative debris in
channel may slow flow
during rainfall events.
Culvert requires
�4 maintenance.
i .
Photo 5
Description
View of channel near
undeveloped town
property on northern side
of Calabash.
. Drainage Concern
" - Channel is not being
utilized to its fullest
capacity.
t
Photo 6
i "t- ix
,,a,,__.�.�.
Description
View of roadway culvert
at west end of channel
-''
near undeveloped town
I`
property on northern side
AL
N`4a-k
of Calabash.
�`„r."`.Drainage Concern
ili�sr�i� -CW?i, .�-� ti Roadway culvert should
be evaluated to
accommodate any
increases in flow.
1 ,-i S /c--_ ;• G 1. L.-]�hl� -� -,�•
0 06428581october 16 photosVormatefthotos 456.doc

Now
Photo
Oemchption
Drain pipe at northern
aide ofGa|taire Village,
ditches converge here
and flow into Carolina
` Shores channel.
^ Drainage Concern
Drainpipe and drainage
area fills during rainfall
oventa, backing up into
Saltaire Village.
Description
Carolina Shores ditch et
northern side ofSa|toine
Drainage Concern
Channel not functioning
om64mmm=w»er`o cvm=

Photo 9
ii
„ Description
Channel flowing from
pond at Saltaire Village
entrance into Carolina
Shores channel.
R Drainage Concern
Severely eroded in
sections with evidence of
undercutting.
�1
x
� .
�Y
G �
} y.•�'
1. a9i.
fit
� r•N ; �-
Photo 10
Description
Northwest view of
roadside swale along
western side of Harbor
Drive.
Drainage Concern
Flooding on Thomasboro
Road. Blocked culvert
preventing flow from
south. Swale contains
debris and unsuitable
lining.
Q:\06428581october 16 photos\fonnated\photos 9_t0.doc

Photo 11
Description
View of culvert and ditch
convergence at west side
c
of Harbor Drive.
r
Concern
X
Drainage
-
c� sue: s'
Ve etative debris and
g
l
refuse blocking channel.
Culvert under roadway in
-. -
need of maintenance.
- � sic r� , y ' �' •:-�
Photo 12
r< ��' r Description
x
40
Closer view of roadway
culvert at west side of
Harbor Drive.
IL
a r„c
Drainage Concern
Culvert is not functioning
properly.
s= l.�,�,' �•
Q.06428581october 16 photosVormetefthotos 11 _12.doc

1
1
1
1
1
1
1
j►l 41111111'WDesc
to 13
rip
'- - Alternate view of ditch
1r. and culvert convergence
r
at west side of Harbor
A,
Drive.
s y Drainage Concern
Vegetative debris and
refuse blocking channel.
Culvert under roadway in
need of maintenance.
Z,��.,�
All
t•
f /
``>. s Photo 14
Description
'sit Channel at north side of
Village Green.
Drainage Concern
Channel may have
otential for increased
' � "''' F• � s�'t:= utilization in diverting flow
from Village Green.
s'd
4-1
dam• 4 1
3.1A,
'sue
•° 3. �,,!'�r 1, 'N� a.. ��+ "'i,:;'
Q.06428581october16 photosVormatedlphotos 13_14.doc

Photo 15
Description
Pipe system on west side
of Village Green.
Drainage Concern
Pipe reduces back up in
Village Green. May need
re-examination when
evaluating Village Green
problem area.
QV64285ftetober 16 photoslfocmateMphotos 1516.doc

Photo 17
ui
Description
�}
's'
Inlet to storm drain on
north side of Highway
179, near the Tropical
Adventure Mini Golf.
Drainage Concern
Storm drain should be
r
j
monitored for proper
.<
functioning.
f i ,

Photo 20
Description
View of outfall to channel
near Calabash River.
Drainage Concern
Upper discharge pipe
may create erosion
problems. Design to
accommodate flow with a
singular pipe.

-
OZ Y'
Photo 21
Description
View of Callahans
property; from southeast
d corner. Naturally -formed
swales drain to this
corner of the property.
Drainage Concern
May be utilized as a
detention pond/water
feature area for new
development.
Photo 22
Description
u Alternative view of
Callahans property; from
' y ' southeast corner.
Drainage Concern
- May be utilized as a
detention pond/water
r 1 feature area for new
development.
Photo 23
• •
Alternate view of
from
Callahans property,
_gym - n/ .. ~ - ..'� • -- i L`.... ^� a, southeast corner.
Drainage Concern
May be utilized as a
detention pond/water
feature area for new
development.